We got our Honda 3000 so it could run the air-conditioner when the dogs got too hot. We can get by with a fan. Otherwise a 2000 would have done.
However, we never had a scenario for leaving the dogs in the rig with us gone that long as in the OP's scenario.
If it were that bad, if circumstances permitted, you could also leave the dogs in their kennels in the truck, engine running, with its air conditioning on.
It is all about scenarios. We know about tossing a dog into a tub of cold water when the dog gets over-heated at events. :( Silly things- they don't know when to quit! :)
