It is about a 38 mile ride, all downhill and can take 4 hours. Yes, a snowman, yes out of snow. The view from Hilo town is very pretty. A trip up to the summit is amazing - and even if you don't want to play in the snow, the views and the observatories might be worth it for you. All the islands have the kind of wide open spaces and rugged terrain that makes a horseback riding adventure memorable.
Lessons are available too.
Go parasailing I haven't tried this yet, but I see the large sails on the ocean all the time behind the boats. I can't decide if it looks like fun or torture yet to be lifted 400 feet above the ocean and pulled behind a speedboat. Well snuba is kind of like scuba but the tank is not on your back - it is carried on a float on the surface of the water. You and it are attached by a very long tube. The training required to do this is very minimal but you can skim the bottom and not have to come up for air - amazing experience.