To think DP should have made the same effort for DD?

[RayFish]

DP took time off work yesterday to take his DS from a previous relationship back to school on his first day back as he wanted to be there to see him off.
Our DD goes to a different school and went back today and DP hasn't taken the time off to go with her as he "can't have time off on both days".

AIBU to be upset at the principle of this? I feel like he doesn't put as much effort or value into DD and doesn't make the same effort for her. She's quite young now so doesn't really notice but I just feel hurt imaging him doing this when she's older and more aware.

I've told DP how I feel and he has just said it's not his fault that he can't have the time off on both days and not his fault she went back a day later. He thinks I'm making a big deal out of nothing. Maybe I am, I don't know. I just think it's quite hurtful.

Think of all the things he does with dd but misses out on for his ds.

Not trying to be rude but have you read the OPs posts at all? She clearly said that her DP doesn't do anything "quality" with his DD at all, she only gets family time when DS is there

My DD has her dad "every day" but she doesn't really does she. He works all day and by the time he finishes she has a bath and goes to bed. When her sisters are over it's all about them, so no I think the whole "she has him to herself" is completely unfair.

If going to school is a "non-event" why did he take time off to take his DS when his Ex was taking him anyway?