For 3 years of age, I would recommend the Garfield Summer Camp area. Great fun for kiddos. There is also a kids wet area on the north east side of Boulder Beach past the last wave pool. The lazy river is great as well!
The entire park is family friendly. However 3 yrs old even at a carnival your lucky to find 1 ride that is geared towards someone that young. However when I went ( last year) I saw plenty of babies of all ages.
Thanks! Your answer is awaiting moderation.