I guess it would depend on what you use for a form or mold. If you use something that isn't flexible (hard plastic, metal, etc.) it should be OK to move them, but I'd still be concerned about large bumps in the road. The size would also factor into it. The smaller they are, the better they will travel. Hypertufa starts to set up pretty quickly. If cracks form from moving them several hours after you make them, I think the pots would always be weak in that area and prone to break. I don't think you'd be able to moosh them back together well enough if they broke - they might look OK, but the strength would be compromised. The pieces really are pretty fragile until they set up all the way. Even after 24 hours when you remove them from the mold they break easily.
Assuming you're using rigid forms/molds, what I would do is have everyone bring a heavy cardboard box lined with a bunch of old towels or rags and place the pots in there for transporting. That would help a bit to absorb any bumps in the road.
Good luck Jill - sounds like a fun day!!
Have a really great time and be sure to share some pictures too!
