Hello Anastasia! Welcome to the Disney Parks Moms Panel.
I fondly remember holding my 18-month old boy on my shoulders during the Festival of Fantasy Parade, the expression on his face when we first saw "the Big Cheese" at Meet Mickey Mouse at Town Square Theater and laughing hysterically when he met Donald Duck (his favorite) when dining at Chef Mickey's at Disney's Contemporary Resort.
Start by introducing Disney characters to your little one before your vacation to get them more comfortable for potential Character Meets and to find out the character that your child will be most keen on meeting. After that, I would make it a priority to find out where and when that Disney Character Meets Guests at Walt Disney World Resort and build around that experience.
By browsing the Planning for Pre-School Kids & Little Ones, you will be able use the prioritized Character Meet as a starting point for scheduling many more exciting attractions and entertainment.
I also recommend Dumbo The Flying Elephant as an experience "not-to-be-missed" for little ones for not only the ride experience itself, but for the excellently themed indoor play area before you ride.
Be sure to take advantage of the Baby Care Centers at each of the 4 Walt Disney World Theme Parks for a quiet rest or feeding.
Have a Magical First Visit!
~Todd