Is this good for 3years old?

Yes if they really like Dinosaurs. Though the shows might be above their age in some cases. Our kindergarten class went on field trip there and the 5 year olds learned a not. Not much to climb on if the 3 yr old is very active

I think it's dependent on the child. I took my 2 year old and she LOVED it but she's SUPER into dinosaurs. There's a big sandbox that's a big hit if your child is into that (I had to drag my daughter out of it lol). There's a station for coloring and the shows, though a little above my daughter's head, we're entertaining enough to keep her still for a bit, especially the T-rex feeding time. If they like running around and stuff, it's definitely worth a visit.