Thanks for all the replies; definitely getting some good ideas here.
I didn't mention our two canine companions on the camper floor. Closing some of the windows might help us, but at least we humans can sweat. Still may be room to experiment here, although getting out of bed to perform those experiments doesn't help the situation.
I know the gel toppers get great average reviews, but I always check the 1 and 2 star horror stories too. Like KansasKen, many claim the gel pads make them hotter. The wool fleece looks intriguing, as does the Sirocco fan.
Looks like it's time to break out the credit card. Thanks again all.