I've read so many stories like this I feel like I'm setting myself up for disappointment on check-in, but at the same time, hesitant to just give points away for no reason.
Have you ever called ahead of time and seen about a pre-checkin upgrade? I read on other boards built around the SPG program (not specific to Disney) that status members had done this and had some luck doing so.
Are your upgrades always to bigger rooms, or just "improved views", etc? I gotta be honest, I don't anticipate ever being in the room enjoying the view - I'll be either in the parks, at the pool, or likely passed out/trying to get my kids to sleep (and a great view of Fantasmic isn't going to help that anyway!!)
I've never called ahead to see about upgrades domestically. I have internationally and had some success but that's such a totally different mixed bag...
I go to check-in and just ask if their is any availability for upgrade for members or for a preferred rate. I ALWAYS phrase it like that. It gives off less of an "asking for something for nothing" and sometimes, they'll tell me I've been upgraded already to a better view/bigger room, etc. and then go on to tell me about even better upgrades with some cash thrown in (usually like $50 a night for a room that went from the worst to the best). I can honestly say I've gotten every kind of upgrade ever through SPG - CL, suites, views, etc. I've also gotten nothing or spent a week at the W on Lexington overlooking an ac unit and hearing the sounds of the trash man. So, if its really important to you - upgrade before. I'm pretty roll with the punches and its kinda a game with me at this point - what can I get or what can buy for a steal! I've also had a LOT of free deliveries at SPG properties all over the world including the Swan and Dolphin. For instance, my last girls trip to WDW - late Fed. 2013, they apologized they didn't have any available upgrades and sent us champagne, fruit, brie, chocolates, a whole crap load of things. It was such a nice guesture, but I don't go expecting a gosh darn thing, so if its important to you then go ahead.
Ugh, sorry to ramble, got lots of free time until Monday, but the point I was getting to is the one thing I notice with SPG and now with Marriott as I've been having to stay at a lot of them recently, is that upgrades are all about occupancy and checkin time. Sure, they can't upgrade you when the joint is packed, makes sense, but it also has to do with the type of packed. If their is a conference going on you can pretty much guarantee you won't get upgraded to a suite - those are all going to be taken by the corp types hosting small events or for workspace, but you might get a view upgrade. Don't check in super early, but don't wait until check in time. I think 11ish is a great time. Tell them you can wait for a room if they have any availablity opening up later. And NEVER ask for an upgrade when check in is busy - or well, I guess you could, but its never happened to me. They don't have time to look through inventory when their is a huge que, and I've seen it, definitely at the Dolphin. One of the times my now DH and I got the mega upgrade we checked in pretty early after a late night stay at the Hyatt and then taxiing over to the Dolphin to make RD at MK. There was NO one in the lobby, maybe someone buying a pastry. I think all 6 reps helped check us in as they were bored. If it matters to me a little more (like on vacation vs. business) I've even just stored my luggage and gone back after the rush. I save time waiting in line and feel like it ups my chances.
Again, sorry this is rambling and sorry I don't have a more definite answer. I don't think there is a definite answer even from us poor road warriors

I know you'll love it at the resort though and the restaurants are really some of the best on property - the drinks at Bluezoo are especially amazing. My DH gets a little misty eyed when we talks about their Manhattans.