I'd really let your kids lead the way. We went this past October with DD who was 27 mos. I had no intention of potty training her until we came back. But at 23 months, she started to show interest. I tried to fight it for several weeks but DH insisted she was ready. Her pre-school teacher also thought she was ready, so I gave up and we started potty training 10 weeks before our trip. I thought for sure we were setting ourselves up for disaster on our trip. But, it only took 4-6 weeks before she was consistently dry and accident-free. No accidents the whole trip and we never had to jump out of line. We just asked her if she needed to go after every ride/show.
It would have been easier if she were in diapers, but only because we had our 6 month-old, so we were going to the baby center anyway. I think a child who is "done" potty training is easier to deal with than one in diapers, but the diapers are definitely easier than being in the midst of potty training.
So, if your kids are ready before your trip, I wouldn't hold them back. However, I certainly wouldn't push it either.
Good luck!!