Thanks all for all the insights! We don't have the thermal pack and while I've considered it, I don't know that the investment would be worth the minimal improvement. I knew it wouldn't be much better than a tent sound-wise, but what I hadn't accounted for was the fact that we're up above everyone else where the sound carries on unobstructed.
Certainly, one of the major draws of the FWC was our ability to "get out there" and away from others...or at least others who are more into camping for the large amounts of alcohol and late-night parties. But with racing...well, I need to be near the race. Generally other mountain bikers are pretty considerate, but occasionally you do get the odd parent of a teen who is racing that's overserved themselves. I've tried it all...tents, a toy hauler, a class-C RV, and our 1968 VW Westfalia. None of them have really fit the bill for what we need.
As for sleeping 4, we've done it once and it worked fairly well. I was up with the kids on the over-cab bed and my wife got better sleep down on the couch. Long term, the Rhino Rack batwing awning we have has the ability to add walls (we have one, saving up to buy the others) to make a sort of add-a-room for the kids to sleep in.
At the end of the day, I'm trying to avoid us having to buy a travel-trailer, which is what my wife would like to get again. I can't see getting rid of the FWC as it just works too dang well for me, but she is adamant that for family trips we "need" a better sleeping setup and a bathroom. 
