I'm just curious as to what other people would do in this situation. I know it's a bit vague!
If you had 2 DC (different dads and not with either of them), one a toddler and one an adolescent, and the older one had an evening appointment, would you ask the older DC's Dad to take them to the appointment, or would you ask the younger DC's Dad to look after their child so you could take your older one to the appointment?
I hope that makes sense!