The interesting discussion about the actual scientific plausibility of the holodeck aside, I believe
Canuck69 was asking is there canonical basis for her story idea.
From one fanfiction author to another, the answer is yes. The second season episode "Elementary, Dear Data" gives you a clear canonical basis for having two or more people on a holodeck using the same program while seemingly located in two different places. Go for it!
Once you finish the story and post it, I'd appreciate it if you would PM me with the url. You've piqued my curiosity and I'd love to read it.
Warmest Wishes,
Whoa Nellie