We have 3 scheduled for our short 3 day trip -- Chef Mickey's for dinner, O'Hana for breakfast, and LTT for dinner. We have O'Hana and LTT on the same day -- we're having a late breakfast and entering the MK a little early for dinner. We're going to the P&P Party, and I want to make sure we're well-rested.
LTT is a bonus, and gets us into MK a little early. O'Hana is a must for our Stitch fanatic, and Chef Mickey's seemed like a great way to start our vacation.
I've also told ds we are not standing in lines all day waiting for autographs. If there's someone unique, sure. For someone he's already met, not happening this trip. With these reservations, he should be able to get the top 6, plus Lilo & Stitch. Plus, I will let him get the P&P characters that are repeats, for the different costumes. He's not into the princesses, so I think it should work out fine.
To answer your question, I don't think 3 character meals is too much. You can control the level of interaction so it's comfortable for your small child -- and you will get to eat real meals!