In my humble opinion...2.5 is a great age to go to the Magic Kingdom.
1) They are free.
2) They are free.
3) They know the characters.
It was great because we would walk through the park and Josie would spot a character and yell their name excited to go meet them. We visited the park last year at 18 months and I felt I was having to instruct her to identify everyone. "Josie this is the winnie the pooh ride...it is fun. And it cost a lot of money for mom to ride this, so you need to enjoy it....ok? ok!" (jk...i am not that cruel...but the thoughts in my head are)
This year I took a different tactic. We focused on being present for all the parades and visiting every character that she likes. SCORE.