How do you travel with pets, as in RV’ing in a conversion van?

Concerns are leaving pet in car. No generator for air conditioning or heater.
I'm thinking more on what can I do with my pet if I am traveling and I would like to go to a tourist attraction ... like a museum or zoo or something for a few hours? Conversion vans aren't large enough for a generator like a massive RV is. I'd like to travel with my dog, but I'd like to see more than just the scenery. If it is too warm or too cold to leave the dog, I could keep the van running, but by doing that, I leave the chance of having it stolen.