I went to Jamaica once and that was enough. I didn't care for the pushy locals preying on travelers. "Go away" after several "no, thank you's" was constant. It was so unpleasant, I can't even recall how nice the beaches were or weren't? It's been a while. You can often get interline rates on interlinetravel friends and family but I can guess they'd be better served doing an apple vacation or similar pkg than adding air on their own. What's their gateway?
How old are they? Are they interested in doing alot of stuff or just vegging? Have them check airbnb.com for private rentals as well as mega-resorts like Secrets etc. Of course, late Sept is early part of hurricane season...choose location wisely.
Hey, that's a start and happy to advise more as info rolls in...