Thanks to everyone who gave advice for this trip - esp CRRF4L, WDWKOOK and mickeynut1. I thought I would let you know everything turned out wonderfully. I will try to limit my comments to Club Level related things.
GF
We arrived on schedule at GF - we got a plain white parking pass and someone greeted us at the front door. Our room was not yet ready, but our CM asked us if we wanted to checkout the SL building anyway. We declined and decided to just check in at the GF lobby, it was nice to be sitting down on the sofa and listening to the piano music while checking in. So we did not get the golf cart ride. My folder contained all the events I had booked at GF, even though I booked them through the BWI IPO (As you know I switched to GF very soon before leaving so I was never able to contact them except to give my arrival time.) We decided to head to MK right away and as soon as we got on the monorail I received the text that our room was ready, so that was nice to know.
Quick question - what is the wonderful scent in the GF lobby?
Btw, At MK, it was One More Disney Day at MK and although the crowd calendar said "2", I expected it to be busy but we must have hit the afternoon lull - we walked onto Buzz Lightyear.
On our return to SL we met Janice, the wonderful CM at SL. We got room number
6421, which was on the 4th Fl but not too far from the elevators, just off the main "courtyard" rooms . It was quiet and facing the lagoon. No audible noise in spite of being beside the Ice Machine Room. I guess no one needed to use it, being at Club Level and all

As WDWKOOK said, the construction doesn't affect SL at all.
From then on we only used the boat to go to MK. On our first morning the boat was empty and did not go on to Poly as usual. Instead the driver took us directly to MK so I felt like we had our own private water taxi. DH was amazed. We always managed to catch the boat right on time upon leaving MK as well. Couldn't have asked for better timing!
My DD's ADR's worked perfectly. We returned via boat from MK to do the Wonderland Tea Party, after which went swimming. Loved the waterfall and slide. Following morning did the Pirate Adventure cruise which is right outside SL building on the dock side. We could see the pirate boat from our room. This was amazing as I didn't even know this was going to happen. So we picked her up after the cruise at 11am, and she was able to have a quick snack and drink at SL on our way to the car. So glad we decided to switch to GF for this trip!
We also used the Disney luggage service for the first time. So we didn't have to load our bags into the car. We called for the bellman at 10am, he gave us a ticket and we collected our luggage at BWI after returning from HS. It was so easy.
On our last day at GF, March 2, the monorail interruptions started. A CM at the gentlemen's wear store first mentioned it to us and said it would be until the end of March. We were glad to be moving to BWI that day!
I have to say we really liked the SL lounge and their CM's. For some reason on this trip I needed more help than usual with my reservations. I had to cancel Narcoosee's last minute and change to Citrico's, and they did everything a few hours before, including changing my Mouseketeers Club reservations. Thank you Janice and Grace. Yes the lounge was quite busy. A lot of families with young children taking advantage of the snacks, but all well behaved. The food and refreshments were always plentiful and varied, constantly replenished, and the tables were always cleared right away. So in fact we never did have to wait around for a table even at peak times. One thing I noticed is that they are not too strict here about the serving times. For the evening snacks, I noticed they kept the food out up to 20 minutes or so past 7pm as long as there were people coming in and eating.
I did visit the RPC lounge. CM's were all lovely here as well. It is a more private lounge feel and quieter as well. There wasn't as much seating as I had imagined though, but I guess there is seating on other floors too? Does it ever get busy here? I hadn't realized that GF 3rd, 4th and 5th floor are all CL? Do they have regular rooms in the main building, and if so, I can't see where they would be located.
In general we felt GF lives up to its flagship reputation. We will definitely return! (if we can still afford it!)
BWI
I won't comment much on BWI since we have been there before and love it. We always love coming back here. We arrived at noon, got our yellow parking pass and were brought upstairs to check in. We got
4261 (yes it was confusingly similar to our other room). I remembered that someone had gotten this room before and although DH was not too pleased at being outside of the Innkeepers Club door, we were very happy with our balcony. I think it may be the biggest balcony facing the Boardwalk! I had requested a full balcony near the elevator, and thinking about it, that's exactly what I got. We just marveled at the view from our balcony. (Now I think I got a room last year which was two doors down, really facing the courtyard but still with a boardwalk view. And it was not CL.)
Do you know how many such CL rooms there are outside the club door? We normally like the restricted access, but I noticed that quite a few people seemed to be coming from outside the Innkeepers Club, so I'm wondering exactly how many rooms are outside.
My only comment about this room is that at night there is an audible humming sound which I think is the Flying Fish AC. It didn't bother DH at all but I could def hear it. I think it may be more noticeable if you're used to a very quiet sleeping environment. But really it's only noticeable once all the boardwalk noise dies down and since you're on the Boardwalk some noise is inevitable.
The lounge was immaculate as usual, and quite empty. The CM's said they would be very busy in the coming week (this week). Even the breakfast rush did not fill it up completely. At night, we did have dinner reservations and didn't see how busy it got after 6pm. But it was pretty empty at dessert time and only really got busy near the fireworks. Not very busy, just 2 other families aside from us.
For all meals, SL had more to offer, but we were happy with the new menu at BWI. They still had the apple and caramel dippers which my DD loves. I don't think I noticed a major change except I didn't see the garlic spread, and there are more salads type food. For breakfast, although SL has a bigger variety, I prefer the hardboiled eggs at Innkeepers Club to the breakfast meats at SL. I just thing eggs are more of a breakfast food. But BWI did not have toast, only bagels and croissants. This is aside from the usual danish and muffins.
Comparing the two lounges, SL is definitely busier and BWI more intimate. But both sets of CM's are great and very friendly. I think that BWI the other guests are more likely to chat and be cordial bec of the quieter atmosphere.
So thanks to everyone's advice we had a wonderful trip. I was happy to have made use of the concierge services which I normally don't do as I book my own ADR's. Having an actual person to talk to really does make a great difference when you are changing your plans around, etc.
I will post some photos following.