Well, I think you will have to rent 2 rooms, as I don't think any of the resorts allow 8 in a room. That said, where you stay really depends on what you and the kids like and how much you want to spend.
Royal Pacific is generally the least expensive, but the rooms are smaller (probably not an issue if you're getting 2 rooms anyway), and no pool slide. Judging by pix I've seen, though, the pool is very pretty.
Hard Rock Cafe is usually in the middle price-wise. It is the best one for closest walk to the parks (5 minutes), and has a really fun pool slide and a "cool" atmosphere your older kids (and maybe Mom and Dad) would enjoy.
Portofino Bay is the most upscale and the most expensive. The rooms are much bigger, it has a neat looking pool slide but a long walk to the parks (you would probably take the water taxi instead, which isn't a bad thing).
It's up to you! Good luck deciding!