Sorry - haven't been in the nearby state parks, but did enjoy Colter Bay. There were motorhomes of your length there, lots of pull through sites (gravel) with full hookups. The lake nearby is relaxing and we enjoyed the ranger talk with our family. Best wishes in finding more detail on the state park options.
A bit about our trip is located here:
History: '08 View, '05 Chinook, '01 Jamboree 24D, '78 Apache Popup, 81 Komfort Tlr,
84 Mazda B2000 'w canopy,
Tent from wedding shower in '96