First be sure and get them a weight they can handle easily. It is hard to beat shooting the bow themselves and seeing how they handle it. Diamond has some Great starter bows and are usually accessible in most places. BowTech Soldier & Sniper are good starter bows as well.
Other bows you might want to take a look at are PSE & Bear. IMO the Diamond Razors Edge is one of the best starter bows because of the extreme adjustability in both draw length and draw weight. All at a price that is well within most peoples budgets.
Dan