Used perperly with the blade perpendicular to the hull the scraper should not damage the gelcoat which is mmuch harder than the bottom
paint that you are removing. That said the chemical stripper while a lttle more difficult still works quite well.
Without seeing the boat it is hard to answer the question about the gelcoat condition. There are a number of ways that bottom
paint can be applied. Traditionally,the bottom is preped by being washed with a solvent to remove any wax reside and then sanded with a moderately fine paper (180 or so). There are also "liquid sandpapers" which are a brush on surface prep. (Not my idea of a first class job) In that case the gelcoat might not have been sanded. Either way, adding new gelcoat is not a job for an amatuer. There are barrier coats that are made for coating bottoms and protecting them from blisters and the like but these are not visually attractive.
I sort of like the idea of stripping the existing bottom
paint and applying a hard bottom
paint designed for in and out use. You should be able to get attractive colors and a slick enough finish to not hurt performance too badly. That way if you leave the boat in the water for a little while you won''y have fouling problems as well.
Good luck
Jeff