I have 3 big Toy Story fans myself! We were able to meet Buzz, Woody, and Jesse outside Al's Toy Barn in MGM. This seems to be the regular place to meet different members of the TS gang. Also, Buzz was outside Cosmic Rays restaurant in Magic Kingdom every day that we were there. This was in November.
Also do not miss the Buzz ride in the MK, he will love it and want to do it again and again. (Actually, you all will, it's alot of fun!)
We stayed at the All Star Movies resort just for this reason. It was our first time staying at a Disney hotel and we were in the Toy Story section. It was amazing. The kids loved the HUGE Buzz and Woody, there was also Rex, Bo Peep, and an RC they could sit in.