Check out the Nerf Super Soakers:
I got Papi a pair of these Hydro Cannons so he could have some lovely bonding time with his children. [Don't mind the negative reviews of the Hydro Cannon -- for an adult, the pump action is easy and it delivers a good blast of water. Ask me how I know.]
Thunderstorm might be the way to go. Extra clips are a must.
However, it's no fun to play by yourself. So get him a pair, or better yet, buy something for the kids that will be dwarfed by dad's power. Life's a bitch, kiddo. This two-pack of Hydro Fury Water Blasters should do the trick.