We travel with just one dog. We favor state parks, National Forest Service (NFS) Campgrounds and Corp of Engineer (COE) parks. I search extensively for our campgrounds and I have found a few of those mentioned above with full hook-ups but most have water and electricity only. Most have dump stations available if no individual sewer hook-up.
I use recreation.gov for the NFS and COE and the individual state park websites for state parks.
Most COE parks just say "domestic pets" allowed. Also, if you are 62 or older you can obtain a senior pass and the cost is half price. I recently booked a full hookup site on a lake in Illinois for just $10.00 per night!
Happy and safe travels!