OP, I think that because you will be on your own, that adds to some of the complexity because it means that they will spend a great deal of time unsupervised.
Given that, I would most definitely crate them in a stall or in a cool shady area with water. That way there is no risk of escape and causing injury or damage (assuming they can’t escape a crate!) to themselves or others.
If you can find a dog daycare or kennel nearby that offers day rates that might be even better as someone else has noted.
I just think if it were me I would not want the added hassle to an already hectic and busy day. I would pretty upset if the dogs got loose and caused havoc.