Am I wrong for not attending my SKs games when DH isn’t there?

I have two SKs(10 and 5), and they’re both in multiple sports right now, so weekends can get pretty busy.

For context, BM is the one who signs them up for all their sports and schedules everything. Because of that, we have a system where she always handles picking them up from our home (if they’re with us) for games and practices, even if we plan to attend. It avoids confusion about transportation and keeps things consistent.

We go to their activities when we can, but DH has to work some Saturdays, which is when a lot of the games are. When he’s working, I typically stay home or go out and do my own thing while the kids are away at their practices or games.

The last time BM came to pick the kids up for a practice, she asked me (repeatedly, to the point where I felt guilty) to come along because no one would specifically be there watching her son during one of his games. It caught me completely off guard,I already had plans and wasn’t even completely ready to leave the house. I felt really put on the spot

Now we have another full day of games coming up where DH will be working again, and I have a feeling she might ask me again. The thing is, I’m not comfortable being around her one one one for extended periods. She can be rude and has made unpleasant comments toward me in the past, so our relationship isn’t great. Because of that, I only attend games and practices with DH. (I also feel like managing games and coverage should fall on the parents.)

I love my SKs, but I don’t feel like it’s my responsibility to step in last minute, especially without any notice. Am I wrong for setting a boundary and only attending games when DH is there?