Are you able to park in the shade? DEFINATELY do that, and crack the windows (course that's a no-brainer). You can also get two rabbit water bottles and fill them up almost all the way and freeze them. Then hang one on each crate door in the morning, so the dogs will have water all day and hopefully since it was frozen to begin with, it will stay semi-cool longer. I've heard mixed reviews about giving them a damp towel to lie on. Check on them as frequently as you can throughout the day, so if either of them starts showing signs of heat exhaustion or whatever, you can get them taken care of immediately.
Would it be at all possible to take them indoors with you at any time during the day??
Would it be at all possible to take them indoors with you at any time during the day??