This Summer I took my 2yr old and baby twins to the following places and would recommend them to anyone with little ones. The places aren't large so little legs can get round. The food is OK but you can take your own. There is lots to do and see.
Lappa Valley Newlyn East here Nice food and trains, the 2year old loved this one.
Pennywell Farm here Petting animals, diggers, tractors
Dairy Land here More animals and a brills soft play area, fun food boxes for small people.
Hidden Valley Discovery Park here Just brilliant, trains, mazes and games, although baby changing not so great but clean.
National Marine Aquarium here lots of fish and a play area, food a bit pricey but toilets clean.
Got my twin buggy round no problems and all the staff willing to help and friendly.