If this is a 1 and done trip like you think, then have your wife drive another car. However, as the kids get older, you will be faced with them growing in a constant confined rear seat. Thus, a bigger vehicle or a constant 2nd vehicle will become more often included in the vacation.
If the truck you have works well for your family needs most of the time, don't make a big purchase just for this trip. You will eventually have to replace it as the kids get older assuming they continue to camp.
A crew cab truck is nice, and it will quickly become the family vehicle. You've got a year, a super awesome deal might drop in your lap.