A 24' round pool will be fine for something like black tip reef, white tip reef, bonnetheads, sharpnose, smoothounds or the smaller species like them.
Sandfilters will work fine for large scale shark set ups. I highly suggest them. I'll toss out that you might want to look into using city water to backwash them with, so you don't lose your salt water when cleaning them.
Another thing I'll suggest is a BIG biotower of some kind to help off gas any excess CO2. Usually big (or several) pt skimmers will do this, but sometimes it's cheaper/easier to use a degas tower. It will also help keep your water quality in check.