Are you able to show us some pictures of the damage to the hull? That would be helpful in determining your steps going forward. As far as gelcoat vs. paint, I would go with paint for the fact that it is easier to apply and is an easier job overall. Everything stated by inair is true about gelcoat, it is better used when sprayed in a mold and used in the beginning process of laying up a boat/jet ski or whatever.
That being stated, yes you CAN spray new gelcoat over over old gelcoat. Surface prep is super super important. The wax additive does, in my experience, complete the curing process of gelcoat. Without the wax, the gelcoat surface feels uncured and gummy, although it is technically cured. It is just not an ideal surface. The real pain in the rear about gelcoat is that after it is sprayed, you will spend tons of hours sanding, west sanding, buffing, cutting, polishing, and waxing it to gain that smooth glossy finish. Gelcoat is not naturally smooth and glossy like you see it on a brand new boat. It takes a lot of time and quite frankly, it sucks. This comes from years of riding and racing stand-up jet skis and repairing them along the way. No problems with any of the repaired spots, so long as they don't get run-into again during a race
If I was you, I would repair the cracks appropriately and paint the boat. Paint is thinner and easier to apply as a whole. You can always change it or re-paint it if you don't like it, too. Have fun and good luck!