an example of what I did because of guilt and 'trying to be nice'.
last Christmas I invited my separated H to join me and my kids for the day, gifts and dinner because I was having trouble getting the kids in one place at one time myself so thought he would also (my one son was visiting and trying to see friends and family in a short time). I wanted my separated H to be able to enjoy the kids, esp the one that had come from out of town, I was being nice. He joined us, it was an all right day, not too much anxiety on my part.

come to find out, he later had a Christmas dinner with his gf, her kids and one of my kids and his wife. I found out because he was on facebook still with my mom and pictures were posted. we weren't even close to being divorced yet.

my youngest has yet to even mention the gf to me (over a year) and my oldest mentioned her once in passing in Oct as 'dad's lady friend' who wants a paver patio built.

so, just because you are feeling guilt or want to be nice, it doesn't mean your separated H feels that way towards you. I would take the kids to the program and have a fun night with them and not worry about dad. Did you never take your kids to things without him before? My X was gone all the time, if I'd waited for him to be around to do things with us we'd have stayed home all the time.