Hi! Our ds's first character meal was when he was 15 months old (dd's was 7 at the time). Just about the same ages as your kids!
We have been to Crystal Palace for dinner three times, Breakfastosaurus twice, 1900 Park Fare for character breakky and dd went for the Wonderland Tea Party. Love them all! I beleive they are on my dd's (now 9) top 5 list of places to eat at WDW!
Since we have only had dinner at CP I can only rave about it. It's pricy, but you get a lot! There is prime rib and I would easily spend $21 on a prime rib dinner. The kiddie food is awesome. My kids love it there! It's so open, airy and beautiful!
Go by your family needs. Are you kids good mid-day? Then try CP for lunch. If morning is best, do breaky!
You are going to have a great time! S