I've done a lot of mapping of local mountain bike trails, followed up by making official PDFs of the trails for many local land managers. OSM is a great, great, great way to go with this, but you're right... Lacking the aerial imagery that Google provides makes things more complicated.
EDIT: That said, I have great luck with using something like OSMAnd+ to have offline sets of data that I'd contributed to. It works very nicely for electronic mapping of MTB trails.
EDIT: That said, I have great luck with using something like OSMAnd+ to have offline sets of data that I'd contributed to. It works very nicely for electronic mapping of MTB trails.