Two grown adults going to a charachter meal? What in the world are you thinking? Do you want to look like fools???!!!
LOL, in all seriousness, of course you'll have a great time. The characters will have just as much fun with you (and sometimes more, as they aren't dodging toddlers throwing food at your table).
I'll echo the Liberty Tree Tavern suggestion as a good "adults only" choice. The restaurant is very spread out and you won't generally be forced into the middle of kid-ville unless you want to, and the food is served family style at the table so you aren't running back and forth to a buffet. It's simple, basic "thanksgiving" type food - but if you like that, it's a great choice.
(Also at the Magic Kingdom is The Plaza - you might want to take note of it. While not a character meal, it's a sit-down restaurant that serves sandwiches, salads, and desserts with great prices - for only a few dollars more than a counter service meal you can have a relaxed sit-down lunch or light dinner without having to go to the expense and time-commitment of most sit-downs. I generally go there several times each trip just because it's such a nice, more "adult" break and such a value.)
Back to the character meals, another good choice is Donald's Breakfastausaurus at the Animal Kingdom. It's a lovely breakfast with Donald and the gang at the AK. It's a buffet, but it's honestly the best breakfast I've ever had. They have a lovely breakfast pizza that really impressed me, as well as the more traditional breakfast items (and even Krispy Kream dounts!). The character interaction is good, though because of the size of the place it's not usually as relaxed as Liberty Tree usually feels.
The Castle has gone through some disapointing menu changes, so make sure you check it carefully before you decide. It is undeniably fun to eat in Cinderella Castle, but lunch and dinner now have pre-plated, single meals that are rather restrictive and not extremely pleasing to many of us. The breakfast is still great, but it is extremely hard to get reservations and, again, is rather expensive. I'm of the mind that if you can't get into Cindy's breakfast, try to get an early reservation at The Crystal Palace next door instead. You still get to walk through the empty park if you can get a ressie before 9AM (on a non-EMH day, of course), and see the castle and stop and take a pic of just you and it. The truth I've found is, especially with the menu changes, it can be more fun to have breakfast looking out at the castle rather than being in it (as the view from CRT is actually not very good).
Hope this helps a little in making your decisions. Remember with character meals that you really are paying more for the whole experience, and that for the same price you could probably get superior meals in other sit-downs. I'm not knocking the food, but just be aware that you're paying for the show too so I always think of character meals as special "splurges". The other benefit is that you will know the final cost before you sit down, which makes things more relaxed anyways.
Good luck!
NED