I was having the same issues, where the entire form was being printed instead of the reports that were navigation subforms. I worked around it this way:
VBA:
DoCmd.OpenReport "MY REPORT", acViewPreview
DoCmd.RunCommand acCmdPrint
DoCmd.Close acReport, "MY REPORT"
It's clumsy, but it allows the user to use the print dialogue instead of just using
DoCmd.OpenReport, "MY REPORT", acPrint
and not being given the option choosing a printer, double sided etc.