1. Our plane lands at 7:30 p.m., and I will be flying alone with my three little ones. I imagine we won't get checked in until 9 p.m. or later. As a family of 5, we will be put in Alligator Bayou with the trundle bed. That appears to be quite a hike from the lobby. Will they give us a lift, as I am sure that my three sleepy heads will not be up for a late night walk in the dark?
Erm, I count four of you, but that could just be my brain playing up...

Put in a request for AB if you want the trundle bed, but be aware it's not guaranteed. There's online checkin of course, but no one really knows if this will work any better for requests or not. I'd suggest calling the resort in the morning before you fly and ask to speak to the front desk/room allocators (ask specifically; all incoming calls are picked up by a generic call centre first).
If you can get an AB room close to the main building then the walk is very short, but the further lodges can be a bit of a trek - see Google Earth or similar for an idea of the layout, or there's a map in the first post in this thread. The resort does have pargos (like big golf carts) for transporting luggage around, and if you ask nicely they'll often give people a lift too, but it's not an official service.
2. Will they hold our luggage up front rather than knocking on the door at midnight when it arrives from Magical Express?
You'd have to discuss that with them, not sure what the policy would be, I know there is a cut-off time for luggage deliveries. You could also put a Do Not Disturb sign on the door if it gets too late.
3. My kiddos would like to go to the POFQ pool to see that Sea Monster. How feasible is it to get there from POR w/o a car?
It's about half a mile along a lovely riverbank pathway (takes about 10 minutes to walk) or you could catch a free ferry boat (5 mins journey time, runs every 20 mins or so). You are allowed to pool-hop between POR and POFQ, so you can take a swim when you get there too.
4. If you have a room close to the pool or bus stop, what is the noise level like? What's the noise level here in general? I'm a light sleeper.
POR is quite good in terms of external noise, even the closest rooms to the roadways have trees between you and the buses and the resort is full of lots of winding pathways so you won't get everyone walking along the same route. If you get a ground floor room there is always the danger of a small herd of elephants moving into the room above though, which can be noisy.
5. Do they have life vests for kids at the pool? I would rather not pack ours wet to fly back.
Yes at the main feature pools, but not at the smaller quiet pools. They are free. They are also supplied free if you are hiring watercraft.
6. What breakfast options are there now that I have heard that Boatwright's is no longer serving bfast? (very disappointed about that, even though I have never eaten there) Any fav menu items you would recommend for dinner?
The food court is open for breakfast from 6am/7am, and they do a good selection of counter-service options from bacon/sausage/eggs/pancakes to healthier make-your-own yougurt parfaits, etc. I'd suggest trying to avoid the peak 8.30am-9.30am period if you can as it gets pretty busy and the lines can get very long.
Glad you're finding the website useful, have a great trip!
Andre