We took Alyssa to WDW in October (she was 6 months) and several characters held her (and she loved it).
Due to the bulkiness of the costumes, the characters need to sit down. At Crystal Palace, Piglet pulled up a chair and held her. The same was true at Garden Grill...both Mickey and Dale pulled up a chair. At 1900 Park Fare, Tigger and Pooh sat on the floor with her. I think all of the princesses at PSB sat down and held her (no bulkiness with their costumes, but safer I guess!).
The lines were pretty long when we saw them in the parks, so the characters rarely held her then. But Stitch did sit down with her in MGM. And Peter Pan and Wendy sat down with her by POTC (they called her a lost girl...very cute).
Oh, and we saw Aladdin and Jasmine in Morocco. Jasmine asked to hold Alyssa and she wouldn't give her back! Aladdin must have said goodbye 3-4 times, but Jasmine was in love with Alyssa and she kept cooing over her. I said, "Jasmine there are a lot of other little kids waiting to meet you." And she replied, "That's okay." It was truly a magical moment. (and I'm happy to report, she did finally give our baby back!

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You're going to have a blast!
Amy