I popped in to see a friend today who does the animation for the Bristol Hotel in Corralejo. She said it is strictly hotel guests only at all complexes due to insurance issues etc. Even then the parents have to sign paperwork and agree to stay on the complex themselves whilst the kids are in the club.
Another possibility would be to take a boat trip to the island of
Lobos, view the fish through the glass bottom (if you're on the right boat!), have a wander around and a swim/paddle on one of the most gorgeous beaches. The visits to the island are half days and need to be booked a day or two in advance at one of the sales kiosks in the harbour area or other excursion sales outlets (see What's On link below) (you'll need your passports with you to book and for when you travel as your passport number is used to reserve a ticket for admission to the island). Take drinks and snacks with you, sensible footwear (not flipflops), sun lotion, hats etc. Stale bread for fish feeding. No shops on the island. There is a basic restaurant with a very nice but limited menu, mainly local fish, I seem to remember it needs to be booked in advance but I don't know how you would go about that!
Have a look at the excursions available as they may be other things that appeal more; buggy ride, camel ride at the Dunes beach for example.
This online mag is a good source of info and Maitland can sort out bookings/trips for you. (He's all online now, his shop in Hoplaco Gardens is no longer.)
What's On Fuerteventura
Enjoy!