Dating a single dad - low on the priorities?

[newboyfriendissues]

I've name changed for this as it may be a bit specific combined with previous posts!

I'm dating a single dad and it's mostly going great. I also have two children but mine are younger and go to their dads one night every weekend. At the beginning of our relationship I really didn't mind just seeing him at weekends, we chat all day the rest of the week and I really like him.

I'm just starting to feel as time goes on that I'm slotting into his life and may just never be in his priorities? I obviously totally understand the children are the most important but I also want to feel important.

His children are older (12 & 15) and their routine is less rigid than my coparenting with ex so often we will meet up to spend the day together but he will have to leave earlier than normal as they want to go somewhere or something. We made plans a week ago to spend tonight together (I don't have my children until tomorrow evening and he doesn't normally see his until tomorrow evening to Sunday) and he would stay. He's now saying his eldest has asked to stay over at his tonight so he can still come over but just not stay, and I just feel really let down and a bit stroppy about it if I'm honest! Is this just how it is dating someone with children, I think at 15 he could have just said sorry I'm out tonight but I will see you tomorrow as planned? Or do I just need to accept the children are his priority and take what time slots I'm given!

Thank you all for your responses it's really great to hear opinions from different perspectives.

No his children don't know he is dating, although I think the older DC probably has some idea! He's been single for quite a while and the DC were quite a bit younger in his last relationship (after their mum) so I do think he has been very available to them and last minute plan changes and I obviously don't want them or him to feel it all has to change just because I am in the picture especially when it's early days, I just also I guess don't want to invest lots of energy feelings and time on a relationship that may never really work.

Not seeing eachother during the week is not purely down to me and my DC, but a combination of things his work patterns included, he does see them as and when in the week if they want to.