I was wondering if anyone has experience at staying here in the shoulder season. My wife wants to check it out on the way to or back home from AZ this coming fall and winter.

We prefer cattail cove. A state park in the area. https://azstateparks.com/cattail-cove/

We stayed a week at the Islander Resort on our way south from Alaska. Nice park but when they test the speed boats it can get pretty loud. Apparently if you can get the boat to clock out at 200mph the price doubles and they will do anything to make that happen.

It was early fall and still pretty hot. One of our A/C units was on the blink so we spent most of the time either in the pool or lake or seeking shade. Nice pool, nice people, generally an enjoyable stay.

We spent the month of March there,Havasu Falls rv park, for 2 seasons. The park is nice & clean, but a bit tight for our RW with the wide rear on the truck.
It was a good time of the year, weather was good & spring breaks, with lots of entertainment from all the young people & dads big fancy boats. Surprisingly they weren't rip snorking up/down the lake, but had them all lashed together creating one huge floating platform with lots of beer.
We've also spent a couple times in Port Aransas Texas during spring break, what a hoot.