We have a shelter which we use to sit in, especially of an evening, but during the day we roll up the sides we attach and any slight breeze blows through the mesh and the area inside is generally shaded. Bailey loves water so we usually go out somewhere where he can have a swim or at least a paddle, but we have invested in a cool mat for him for our next trip in a couple of weeks. I had read that it's better to let your dog lay on a wet towel rather than covering them with it.
------------- May/June - Spring Valley
Aug/Sept - Leekworth
Another vote for a cooling coat. We used one over the past 3 weeks in France and found it very effective.
The coat fastens on the dog with Velcro, like a normal coat, and never dried out fully while she was wearing it so was still flexible enough to just take it off. If necessary you could just pour more water on while the dog was wearing it.
We also took a collapsible water bowl and a bottle of water for her while out and about.