You probably won't be able to sell the truck unless you can make up the difference you owe at the time of the sale. If you can't do it then the point is moot.

If you think you have a chance to sell it for the amount owed then advertise it on Craigslist for a little more than you owe. If someone offers you a little less, and if it is within reason accept the offer. Make up any difference at the time of the sale at a title company office. Craigslist advertising is free.

Is the van in better shape than the truck? Is the van worth more than you owe on the truck? If you and your family can fit in the truck then sell the van and use that money to pay for the truck. If you must keep a motorized vehicle you should try to keep the one that is in better condition.

Maybe you could sell both the truck and the van and use that money to pay the truck debt. Then get a small used car for the family. Just start selling stuff and get as much money for your family as you can.

Read the How Simply Do You Live thread and get an idea of how some people live well with fewer things. Maybe your family already lives that way. I found the thread inspiring. Perhaps your wife would too.

Sell the BMX bike "newest toy" too.