It's just a myco flare-up. Cause by the stress from the car-ride and change in scenery. It will go away pretty quickly. If not, some antibiotics would be in order(Baytril or Tylan, works well on mycoplasma).

If they recover quickly, I would keep them. Means they have a nice, strong immune system and can take some stress. If they don't recover, then I would feed them off and get new mice. You want them to pass on the strong genes and immune systems, not the shoddy ones.

They may also be sneezing to get the crappy Carefresh out of their lungs. That stuff is awful. I use a mix of a TINY amount of equine fresh(tractor supply brand) and aspen. No problems here.