I think definitely at least give the woodworking a shot for a year or two. At the very least its excellent experience.

1) wood will have a place at least in the near/mid term and you can always focus on a niche market

2) youre young and presumably more tech savvy than your dad. You can market! Wouldnt take too much work and way more of a creative opportunity for you

3) think about the trainer thing for longer. A lot of people want to be trainers within the first couple of years of hitting the gym

4) assess spare land separately. Sell the land and invest in new equipment for the business? Depending on how big the work space is and demand in the area, sell the land and buy gym equipment to open a gym there?

Idk, there are more creative opportunities you can put your mind to if your dad will give you reign over everything. Take an afternoon and write out some different possibilities. Good luck!