Transfer your miles CO --> Amtrak --> United
Transfer 20k of your wife's mile CO --> Amtrak --> United (And if she gets 2k more CO miles, transfer that 5k block as well)
Transfer 5k of your 5 yr old's miles CO --> Amtrak --> United

Then make sure to earn United miles no matter who you fly -- if it's United or USAirways, just credit the miles to United. If it's Continental, Delta, Northwest, or Alaska then credit the miles to Continental and transfer to Amtrak to United. If it's American or Midwest Airlines, credit the miles to Midwets and transfer to Amtrak and then United. (Note that Amtrak allows each account to transfer out only 25k points per calendar year, so you'll have to wait till 2005 to transfer future chunks to United)

Then get yourself a United Visa, which is available free the first year with a 15k signup bonus (or 20k signup bonus with fee right away). And get one for your wife. And start earning!

United miles are FAR easier to redeem than CO miles!

Although if you choose not to go this route, make sure you don't rely on the Continental website to try to redeem those CO miles as it won't search partner awards. You'll have a much better chance using your miles on Delta than you will on Continental (or Northwest).