I agree with Luna C. Lopez Island is the first stop for the Wash. State Ferry system in the San Juans. You can view the accomodations at the Lopez Islander Resort that Luna C referenced to. For those in your group that wish to camp, the Lopez Islander may possibly be able to accomodate you with that. Otherwise, there is a nice camping area near the ferry landing at Lopez. It is a San Juan County Park named Odlin County Park. This is a very popular camping area and it is advisable to get reservations for it. It used to be (and may still be), that they only accept reservations 6 months in advance. (Reservations are made at the county seat in Friday Harbor). Odlin is approx. 3 miles from the Lopez Islander. In the past when we've camped at Odlin, I've secured a slip at the Lopez Islander and cruised over in the boat and then my wife has brought the van over on the ferry to Odlin. Lopez Island is a very popular island for bicyclists, so if so inclined bring bicycles or rent them on the island. Lopez Island is also noted for its' friendliness, as it is the custom that as motorists pass you they ALL smile and wave at you, so wave back.
The Lopez Islander also has a swimming pool and jacuzzi.
Hope this is a help.
If Odlin County Park is of interest to you, you may PM me and when I get home from work tomorrow, I'll send you the "contact" phone number.
P. S. The town (village) on Lopez Island is approx. 1 mile from the Lopez Islander towards Odlin.