Mickey is wearing his normal outfit in his meet & greet, we're just back from the 25th anniversary celebrations last week
We've stayed in the Castle Club in the past, it's really wonderful. Service there is amazing. Breakfast is yummy, you have a beautiful view over Main Street and the Castle... You can also go back to the lounge in the afternoon for soft drinks and snacks, I really recommend doing it. We found ourselves easily going back to the hotel and our room, to drop stuff off, have a rest... You'll get a key for the Castle Club lift, it takes you directly from your floor to the park entrance.
The VIP fastpass cannot be used all day, if I remember right it was only up to a certain time (something like 7pm, but this was a few years ago) Still, it covers the busiest time of the day, which is the main thing. We did countless rides on Big Thunder Mountain!
You've picked some of the best restaurants. Walt's and Bistrot Chez Remy are the ones to book as soon as you can to avoid disappointment (though you may as well book all restaurants once you call). Blue Lagoon is also really good, but I think it's closed in May (Pirates is closed until July and usually the restaurant closes at the same time). Agrabah is our favourite buffet, we go there regularly, and never had a bad meal. For fast meals, we love Toad Hall in Fantasyland (fish & chips), Cookout Barbecue in Frontierland (ribs....), Hakuna Matata in Adventureland. In the Studios, other than the Bistrot, the only good restaurant is the Cafe des Cascadeurs, if it's open they have some of the best burgers in the resort! If you go to the Disney Village, they've opened recently a Vapiano (italian) and Five Guys (burgers) which are good.
My top recommendation to anyone going is to ride Big Thunder Mountain at night... During the day too of course, but once it's dark, it's even better!! Don't miss Phantom Manor either, and take some time to explore Boot Hill, the little cemetery outside PM (once you exit the ride, turn left to Boot Hill).
I guess you should also ride Space Mountain aka Hyperspace Mountain, it's currently closed and being re-themed with Star Wars (it will reopen before your visit). We're getting new trains so hopefully it will be a bit smoother, but otherwise from what I understand it's very different to the American versions of the ride!
The Studios are... well we'll say they're a work in progress... Nowhere near as nice as the Disneyland Park, but it's getting better. Don't miss Ratatouille (and take some time to admire the whole mini-land around it, it's really beautiful). You can fastpass it so try to get to the Studios early and head straight to Crush (they officially open at 10am but usually they let people earlier, I've seen them queuing for Crush from 9:30am). Also a good show to watch in Mickey and the Magician. I usually spend a bit more than half a day in the Studios (depending of which shows we're watching)
Have a great trip!!