To tell these people that DD doesn't want to go to the B'day party?

[complexo]

So, we were invited to this B'day party tomorrow and DD doesn't want to go...I have already confirmed attendance and I don't want to use a lame excuse...or should I?
They are not best friends, but they are a very nice couple and always invite us to their childrens b'days, christening and etc, I met the woman during a course, and we do bump into each other ocasionally as we live near. Their children are younger than mine, my daughter enjoyed playing with them at the beggining but it has been a long time and she lost interest.
Also DH is palnning for us to go for a meal I thought I could pop in on the way just to wish happy birthday and leave a gift, but now with daughter not going he won't be happy to do it either, as he doesn't know them and is not ery keen on socials outside family...

Why the fuck ask then OP.

Refresh your backside in a bidet [advice]

I don't know why you are being so arsey!
YOU accepted the invite even though you knew DD probably wouldn't know many people - then DH gives you a better offer (or stamps his feet at you) and suddenly it is ok to let this family down.
Are they friends of yours or only friends when you don't have anything better to do?
Your dd sounds like a little madam and you are encouraging this behaviour and making a rod for your own back
Why post in AIBU if you are so sure you are right then get the hump when people disagree with you?

They were described as "these people" in the OP. Am glad she is not one of my "friends".

I guess this means your DD went to the party and probably enjoyed herself. That's fine. Birthday child & family etc all happy. However it sounds as if you only went because your DD decided she'd like to go after all. I still don't think you really took on board other people's views on this AIBU thread.

That is your choice. You might like to ponder on the fact that if you don't encourage / compel your DD to turn up to parties where an invitation has been accepted, then (1) she may not be invited to so many parties in future and (2) other guests may think it's fine to not turn up at your DD parties.

Even if a party is at home, hosts have to think carefully about numbers and how many people they can afford to invite

If I invited you for dinner, I assume you wouldn't cancel on the day, because you weren't in the mood?