Our family enjoys lazy rivers, nice pools, and mini-golf (on-site) when we don't want to go anywhere. We had that in Myrtle Beach at the Sheraton Broadway Plantation last year. We want this for a summer 2009 vacation and we trade through II. Any suggestion would be helpful so we can maybe put in a request.
My family also loves lazy rivers. Especially the really large, winding ones, with a nice current. I don't like the lazy rivers without currents or ones that are so small that they are basically a pool with a concrete island in the middle.
The ones in II I can think of are: Marriott Aruba Surf Club, Harborside Atlantis (at adjoining hotel), Westin Kierland (at adjoining hotel), Marriott Canyon Ranch (at adjoining hotel), Hyatt Coconut Grove, and Hyatt Wild Oak. The Hyatt in Puerto Rico I believe no longer has a lazy river.
The ones in RCI I can think of are: Grand Mayan Nuevo Vallerta, Orange Lake Resort in Orlando, Wyndham Bonnet Creek, Wyndham Seawatch Plantation, Wyndham Ocean Boulevard, Ron Jon Caribe. All of the Wyndham lazy rivers are pretty small.
For II, I think the Arizona resorts are your best chances, as its low season around there. I occassionally see Aruba and the Hyatt Coconut Grove for the summer, but not often.
For RCI (or if you use an independent trading company, direct exchange, or rent), I believe the Grand Mayan and Orange Lake are pretty easy exchanges, but the rest are pretty difficult for the summer.