Well if you are using check-in as defined by "fully & completely checking in, including physically going to your room" - you may have a wait. If you mean what I call "Disney Check-in", you simply go to the hotel, get your room keys, get the welcome to WDW, here are your maps, transportation schedules, etc.... and your room may or may not be ready, in which case if your room is not ready they simply store your bags until you return from the park, or you may choose to have them go ahead and deliver them to your room (assuming that the room is ready) - which may or may not take a while depending on how busy they are. In any event, you can "check-in" as soon as you arrive at the resort- no wait (except for the line) - your room may or may not be ready, but that is not a big deal (at least not for me) I suggest...
Do the "Disney Check-In" - let them store the bags, don't waste time waiting. Head on over to the park - when you get back call Bell Services for your bags. Now obviously there are potential pitfalls, you may need something from your bag - so think ahead & don't put it in there or get it out as soon as you get to the hotel
As far as MK restaurants... there is Crystal Palace (need a PS), it is a charcater buffet and the food is good. There is Liberty Tree Tavern -been a while since I ate there, but I personally don't really consider it a "sit down" restaurant. Then there is the Royal Table in the Castle (definitely need a PS). Food is Ok, atmosphere - well you are eating in Cinderella's Castle, need I say more? If you want to take a dinner break from the park - take the boat over to Grand Floridian - there is a character buffet at 1900 Park Fare. Or you could take the monorail (or walk) over to the Contemporary and eat at the Concourse Steakhouse (PS is a good idea) or really do it right & eat at California Grill - heck just watch the fireworks from there.
Have fun!!!!