Another and almost separate problem is number of horses. Many horses will be quite quiet with one or two other horses but get panicky in a larger group, especially if the other horses are strangers. The best way to approach this is, once yours and your friend's horses are comfortable about waiting, to go out with a small group but stay by yourselves some of the time. You can go along with them, then turn and walk back down the trail, then trot up, or plan to meet them. Gradually accustom them to the larger group, then increase the size of the group.
Gradual introduction is the key.
When my husband was breaking young horses to fox hunt, the first year they went to the meet, looked at all the other horses and the excitement and went home. The second year they went along about three fields behind the others. The third year they hunted at the back and the fourth year they hunted in the middle. Needless to say they were perfectly mannered. It is well worth spending the time to get your horse to be relaxed with other horses and gait changes on the trail.