What kids are the friends bringing? Only daughters? Or will other boys be there. If so then it's not really a mother daughter thing at all and that's not fair to the boys.
I think if they boys really want to go and other boys will be there then you need to pick a different activity for mother daughter time. Then always have a mother son time with dad having daddy daughter time too. It could be a regular family thing to do one weekend per month.
1st weekend of the month opposite kids day. Mom/sons, daddy/daughter.
2nd weekend of the month, family outing. No big deal. A day at the park, cook out with hot dogs and burgers, go to the pool and hang out together, movie marathon of the kids favorite movies, any activity that is low cost and fun for everyone. Families that do stuff together regularly are often closer than families that don't.
3rd weekend of the month same kid day. Mom/daughter, dad/sons.
4th weekend of the month do an hour or two with each child. Coloring, finger-painting, doing a craft, going for a walk, tossing a ball around, doing puzzles, something that that particular child likes that maybe no one else likes to do. Dad and mom can both have this time while other kids are playing or doing their own thing.
5th weekend, March, June, September, and December all have 5 Saturdays. This is a special time that you can plan a great activity. Something that is wonderful and special. Go to an amusement park, go on a day trip, go to a county fair, take a trip to the nearest cool museum or zoo, any activity that is something out of the ordinary.
These can be switched around for sure. We are on SSDI so doing something big at the end of the month would be impossible for us. Even if it's only 3-4 times per year. Saving money for this would be a must. So if you needed to do it at the first of the month that would work too.
The point is that spending special time with the kids is the thing they will remember the rest of their lives. Not the having to do cleaning all day Saturday, not sitting at home with nothing special going on, they will remember the family times and the private times they had with you and dad when you they are adults becoming parents, even long after you are gone. They will remember the times when you took time to spend it with them.
Oh, and take lots of pictures and tuck them into scrapbooks. My MIL was dying and that was her only regret in life. She said she would have enjoyed looking at scrapbooks and remembering special times she had with her family and friends. She just didn't take many pictures. She still had the one of Ronald Reagan holding my hubby when he was a toddler. My FIL was career Navy and knew him slightly. They lived all over the world and she had no pictures of any of it. So take lots of pictures. Of silly things, of hugs, of sunsets, anything that will help you and your family remember those times when things were perfect.