If you hook onto a group ride in Nickerson - that's my best recommendation, going at it alone would be difficult to link up the best trails/loops, since they are not marked on any maps.
The group I have ridden with in the past is a shop ride out of Orleans Cycle. I would give them a call next week on Friday and check in on the ride plans 508 255 9115. They usually ride Sunday AM out of Nickerson SP.
There are usually two groups that head out, a 7:30AM brisk paced group (they start at the lot down at Big Cliff Pond in the park) and a group aimed more at intermediate/adv.beg ride level (Mello pace), they start around 9AM from the bike rental (gravel parking lot) out right off of 6A near the main entrance.
If you are a surf fisherman, bring your gear! The Stripers have just started back at it (Blues too), and next weekend they will be feeding up big time for their fall migration, and you'll be right in the PRIME time for some angling right off Nauset Beach in Orleans (go at dawn or dusk). The false albacore have been ripping it up too.
"Everyone I know in bicycling is at least a little bit crazy, present company included." Sheldon Brown