You can go to Clearwater Marine Aquarium if you go to Clearwater. It is the home of Winter and Hope from the Dolphin Tale movies.

Why not go to Hernando Beach instead?
http://www.tripadvisor.com/ShowUserReviews-g34722-d1125606-r62224751-Pine_Island_Park-Weeki_Wachee_Florida.html

Then you could go to Weeki Wachee too, that is fun.

I wouldn't drive 2 hours to go to Clearwater beach unless what you want is white sand and that is it.
Fred Howard Park is nice to (Tarpon Springs)

We will be in North Central Florida (Ocala area) and I would like to make a daytrip to Clearwater beach with the children (young children). Is there a particular place you have been in Clearwater that doable as a daytrip with young children. The other option is to go to the beaches in the St. Augustine area but Clearwater beaches seem calmer and prettier.