Never stayed at a group CG but some notes:
Always check to make sure RV's are allowed in the group area. They're not always allowed.
Camp Hale East is pretty isolated from the main Camp Hale CG and you get the whole thing to yourself. Also further from the highway and that noise. There are small ponds and streams to fish in the Camp Hale meadow.
Printer Boy near Turquoise Lake is on a loop of four group campsites so not quite as private. Also cooler and can open later in the year due to snow.
Bogan Flats has a group site quite separate from the main CG. Beautiful setting right on the Crystal River near Marble and Redstone. I've never been through the CG but seen trailer/RV tops poking through the trees.
There are a couple of group sites on CO 67 north out of Woodland Park. There are some lakes for fishing up there.
Near Lake Isabel in the Wet Mountains SW of Pueblo there are two group sites. Small to mid-sized RV's can fit up there, but turning a 38-40 foot trailer might be a challenge. The groups sites are well separated from the main CG's. Fishing in the lake. Bishops Castle (free) is worth an hour or two, esp. if there are kids 6-16 along.