Should I ask again or let it go?

This is my sons father and step mother. I deleted the first one because I forgot to add it. He is not involved in my sons life besides when he is there every other weekend. They are getting him more days for the summer but I have to get him early or they just don’t want him because he has sports games that they don’t want to go to. I do everything else including school, sports, drs etc. So I asked them multiple times for their vacation plans and they never answered me. I told them a long time ago about ours so they could plan around it or I could plan around theirs. Ours got canceled unfortunately. They planned a vacation the same time that mine was so they wouldn’t have to take my son (I didn’t know because they never told me). I don't understand! I told them he could go and they ignore me, yet if I don't answer back fast they test multiple times but it's okay for them not to answer me. They told my son they were going to the beach but he couldn't go because I had a vacation that week. My son asked me if he could go with his dad since our bigger vacation was canceled and I’m totally okay with that. I don't understand how they could want to go on vacation with their other kids but not mine. It hurts me for him. Should I ask again or let it go?It just bothers me because there's no way I would take some of my kids on vacation and not the others. It aggravates me that if they didn’t want to bring him they told him about it and then blamed it on me. I don’t know if I should ask them again or just not say anything else about it. My son knows that I said it was okay and asked them about it 🤦‍♀️