You can also ask player to subscribe to the same mods (if its a steam workshop) - it should work as well
As Vizze mentions, it doesn't always work. As I also mentioned in the initial post.
The two methods I've found so far are:
1: Vizze's solution of creating the 7zip file and sending this to my players.
2: Sending my players a list of the mod's, getting them to subscribe at least a day in advance and making sure that they've restarted steam and entered DOS2 at least once prior to the day when I pre-load with them.
Both options work, but do require some added effort on both sides.