Centreville can get rather crowded. Since it's the amusement park of the Toronto Islands, all the kids want to go there to play. As a child, I loved the antique cars. The swan boats were charming also.
Nowadays, I still enjoy Far Enough Farm, which features many different animals, including some that aren't that typical of amusement park farms or petting zoos. They have Flemish Giant rabbits which are amazingly huge and cute. The Silver pheasant is a gorgeous bird -- it has some soft white feathers with delicate black markings that look like calligraphy. The Mandarin ducks were also very cute and have some pretty impressive feathers.
There isn't much to eat in Centreville other than junk fast food that you'll probably have to wait ages in line to buy. I think the best plan is to pack a picnic lunch and relax on the grass somewhere. There are lots of green grassy areas just outside of Centreville on the Island.