We went on the preview day (June 14th) so I can't speak to the crowds. I took my 2 1/2 year old DD. She is really tall (just a smidge under 40" -- they wouldn't let her ride RSR).
We rode Mater's Junkyard Jamboree 2 or 3 times and she liked it quite a bit. She stood in line for Luigi's with my mom and sister, but it was a longish line and after 30 minutes they bailed out. I think they were probably another 2 or 3 cycles away from loading.
They did have the different character cars out and about, but I don't know if that was just for the media. We took pics of her with Red, and she "spoke" to Lightening and Mater (couldn't take pics with them because they were roped off so the media could get shots without random people in them). Fillmore's hut has a small false doorway on the back/side of the dome that has hippie beads flowing down the frame. She really enjoyed standing behind it (hiding), and running through the beads to surprise us. Your child may enjoy that as well. There are a few benches nearby to rest on. The rest of the land was not very toddler friendly, I'm afraid.
All in all, my DD was just as happy to go ride the Carousel and LM, and even though we skipped it that day she always LOVES Bugsland and the water play area.
Hope you enjoy your time!