Flagstaff is seriously lacking in decent RV parks. In my opinion almost all are dumps such as KOA, Kit Carson, Blackbarts etc.
J&H RV is decent, clean but it caters to the retired crowd, lights must be out at 9pm, frowned at if you sit outside with a beer or glass of wine. We were told to take our drinks inside as its not within the beliefs they wish to have for the park.
Woody Mountain is decent. Owners are very nice. It is forested, dirt, gravel roads and spots. Some spots are a bit tight because of trees. Camp fires are not allowed.
Instead we have been staying in Williams 30 miles to the west of Flagstaff. It is a very fun small route 66 town on I-40. Circle Pines KOA is very nice but pick one of the larger spots. We prefer the ones in front of the office area closer to the highway as they are larger. It is a forested campground. Camp Fires are allowed.
Our favorite is Grand Canyon Railroad RV park. It is owned by the Railroad and is next door to the hotel and train station (steam engines, old cars there). The RV park is very clean, modern, wide spots (we get pull thrus). Access to indoor hotel pool, bar, restaurant for RV guests. Easy drive from RV park to Grand Canyon for the day or ride the train for a fun day.