As a field trip coordinator for our home school group this year, I help to organize field trips (obviously, lol). I just realized the 1st big one I organized falls on the day the SKs spend with BM for the month. It was the day available for this trip so I had no choice. In the past, I have invited BM along, on occasion offered to pay her way and even paid it the one time she did go because otherwise she was going to cancel her visitation. She has not tried to go on an outing or EC event for the last couple of years though. But the few she went to prior, she expected me to be right there by her and "hang" out with her. As the coordinator, I won't be able to do that because of my responsibilities. The kids do not know about the trip yet. Would you still invite her to bring the kids so maybe they don't miss out? Or not mention anything to the kids and not worry about it? The trip is still a month away so I have plenty of time to figure it out still.