J & H is the best place in Flag IMHO. We have stayed there and put up with some of the staff and the many rules. Avoid KOA (and I am not a KOA basher in general).
We have also stayed at Munds Park and it was fine - have not been there for a few years. Munds Park is 23 miles from Flag. J & H is east side of Flag and a ways from Sedona. Munds Park would be closer but no easy way to get to Sedona from there - you can take Schnebly Road but is a long and not easy ride due to the road conditions - but spectacular. If nothing else, take it from the I-19 just south of Flag - maybe exit 320 - as the first miles are a pretty good forest road to a spectacular viewpoint. But down from that viewpoint to Sedona is a challenging "road". Have done it but need good high clearance vehicle or a rental car.