So, I'm assuming you'll need a 2 BR. You can rent points from an owner or service or book via Disney direct. DVC is per unit/per night points. The minimum for a week's stay in about 250 points at OKW, SSR, AKV. Other DVC are 300+ points. You can google DVC points charts. The going rate for rental is about $13-17 per point. Much more $$$ thru Disney. Trading into DVC via RCI is usually a 1 BR at SSR. 2 units at SSR would be $500 in trade fees, plus $400 DVC fees, plus exchanging 2 prime RCI units.
Allears.net is a great place to see photos of the different DVCs. Each has a different vibe. I am partial to AKV, where I own, but have stayed in most of them. Those ages would love the animals at AKV and the points charts are reasonable. They're all great IMHO and I'd be happy with any. however, the $ saved by staying in your Marriott (have also stayed in most in O) would pay for a lot of WDW tickets, which are $$$$ now as well. We had years of great off-site WDW trips with young kids before buying DVC. Not trying to dissuade you, just letting you know it's a big investment to stay in a 2BR and maybe not "worth it" IMHO, and that's from a DVC owner. We get a 1BR with a family of 5 and that's worked fine for us--but to go to a 2 BR would not have been cost effective over other very nice off-site places, IMHO. We still trade via RCI for Marriotts and HGVC when we need a 2-3 BR at WDW.