We've been using a Thule Hitching Post for at least 8 years now, and it's sweet! It's real basic, but it does swing down if you want to open the back of your van. Technically, it holds 4 bikes, but they need to fit well with each other. Kids bikes may or may not fit depending on how the toptube and headtube meet. Thule or Yakima now makes a 5 bike rack, so you could really stack them up.
The nice thing is 1 bolt holds it in the receiver, and everything stays away from the back of the van and the tailpipe. Easy on, easy off. If you buy a little nicer model, the arms fold down so they're not so obtrusive when you're driving around empty.
With a big family, I have both roof mounts and a hitch rack. The hitch is definitely the easier one to load. No bugs smeared on the bars or headtube either when it's behind the van. Enjoy Colorado!