Wadi bashing, desert camping (Muscat)

Hi everyone, I am fairly new to Muscat (3 months) but have some friends coming over to visit from the UK. They are interested in trying some wadi bashing / dune driving and desert camping but as I haven't tried these myself yet I am wondering if anyone has any good recommendations for people/companies to go with that offer a good service at a reasonable price.

Any suggestions would be appreciated!