I recently had a great trip out with this company looking for basking sharks. Although they can't guarantee you seeing a shark, they will but a lot of effort into finding one.
You can borrow snorkling gear from them and children can watch from the boat. It is £50 to go out for 4 hours, which seems like a lot, but it is worth it if you get to swim with the 2nd biggest fish in the world! read more