I just used my Mr. Heater "Buddy" on a trip from VA to VT and back. We cracked the side windows while in use and also get a CO detector as added insurance. Worked GREAT, however there were only two of us in the van -- and even then things got tight when/if we were messy.

From the posts I've read, there are two general ways to use these heaters:
1) is to use it to keep the van warm while sleeping. While I'm sure it's OK safe, and even more so w/ a CO detector, I don't like all that water getting into the air (that, and the cold air while I'm buried in my sleeping bag is what I like!)

2) is to use it while stopped at little, before going to sleep or when you first get up in the morning. This is my use and (for me) it's perfect. In 30deg weather (with sun) we ended up shutting the thing down after 10min or so since it got so hot! By that time we had capeline on, wool socks and a hat. Plenty warm.

Sounds like you're in the #2 camp and it prob would work great for you. Have to teach the dog and the kid to leave it alone, and if you're that worried about getting stuff into it a screen could be fashioned easily. That said, they are REALLY warm up close so I'd be careful about resting a foot on it.

I'd vote for asking the wife to give it a try, and if it doesn't work I'm sure Karl has a Plat Cat heater you could install instead. Great heaters, but $$$$ in comparison!

john