Not sure if there's an age limit...
our two were just four years old, and they loved the "playroom" (This was at the BWV Sales Center, and I would assume that the new sales office playroom would be somewhat the same...)
If you're going to call to arrange a tour before you go..just ask If you're going to wait until you get there, one of the reps at the resort would know...
When we toured last summer (at the BWV office), our DS4 and DS2 (at the time) were "allowed" in the supervised kids club area.
My understanding is that normally children under 4 are not permitted, but with prospective DVC-ers, I'm sure they do whatever it takes to accommodate the children and make the sale!