Yes. You can reserve the picnic shelter for $20 per hour during open hours here.
The picnic shelter is the only BBQ in the facility. You will need to provide your own charcoal, lighter fluid and match if you choose to grill. Reserving the picnic shelter does not allow anyone to skip the line on busy days, so make sure you show up early to avoid waiting in line during your reserved time. Picnic shelter rentals do not include admission into the water park.