It depends on what you want in your main display tank. If 100 lbs of live sand is what you want in and it looks good than go for it. I don't think it will hurt. I would go for a sand bed no deeper than 2in everywhere.
It does also depend on the fish your getting, some fish require a DEEP live sand bed, so they can bury themselves in at night to sleep, or burrow and make tunnels for themselves to live in. So again, it's just want you want and what kind of fish your putting into your tank. I don't think 100 pounds is going to be that deep, I put 80 pounds of sand into my 55. It's about 2in sand bad.
Fish Sticks, the best thing you can do with your dead fish.