Thoughts on our seating dilemma

So my fh mother made it clear very early on in our 17 month engagement that she does not want to be seated anywhere near his father. At first we thought she was joking because right before the pandemic he was coming over every Sunday to pick up a plate of food she saved for him. They even came together to book the venue with us last February. She mentions him not sitting next to her a few months ago this year and goes into details of why and my fiancé and I know that she is truly serious. Apparently the father has been playing victim and painting her to be the bad guy to his family regarding matters of unpaid child support or something of that nature. I can’t remember. She is mad because she has never said or done a bad thing to him and has always welcomed her into their home to get food and see their adult children. We definitely thought or hoped it would be solved by now. But she seems really firm on this. Our issue is that we are only sitting people with their family, the ones they live with or their close family. So there would be no other place to put him other than by himself with his 2 other relatives. We have always planned to put my fiancé’s family at one table. This table would consist of my fiancé’s mom, sister, brother, niece, brothers gf and mother of his niece, his step grandmother, great aunt and father. But if we don’t seat them together to honor the moms wishes we would have to move the father, along with the great aunt and step grandmother because they are the fathers side of the family. This would make them a table of 3 at a 10 seater table. Our concerns are how it would look that there are only 3 people at a big ole table, also how it would feel to his father and aunt and grandmother being separated from their family when they see there’s space for them there. We downsized to a 50 person wedding so all other tables are households and close family. They have a small family so there’s no other family table for us to move them to so they don’t feel like such an island. We also don’t want the aunt and grandmother to feel punished by being at a basically empty table when all others have up to 6 or 7. I don’t know if we should ask that they get along for one day for their son or honor the moms wishes. (We’re not even sure the father knows there’s an issue) Thoughts? The seating chart is due on the 28th.