I'm still up because he's not home yet and I find it impossibly hard to go to bed when he's out. Even though I could've easily gone to bed at 9pm... 
The hobby he does is something it is required that he commits to for 3 months at a time, twice a week, and in the final 7 days of it there is a Sunday afternoon and 5 evenings he cannot miss. He didn't think to check which week it was that we were planning the party for, and I didn't think to GET him to check because it's HIS diary and HE should be managing it. It's not that he intentionally missed the party, just can't organise himself apparently.
To be honest I don't think the kids didn't even notice. My parents were there and were a good distraction, and were helpful in that they were just generally around to keep an eye on the kids. DH often slobs off from things I do with the kids. He is getting better at taking them to the park etc when I'm at work (because I keep telling him off for not doing anything with them or going outside at all, and spending hours on his computer), but still often doesn't come with me if I take them anywhere unless basically I tell him to, which I've given up doing coz, y'know, what's the point?
He has some redeeming features, yes. He cooks really well, does laundry at home and some useful things like cutting the grass/hedge, does the school run unless I'm able to (I like to do it when I can). He a great dad when away from the computer. He tries to get the kids to be quiet in the morning on a weekend I'm not at work if I'm clearly exhausted and need a rest (although that never works.) Sorry, I've run out of redeeming features... Oh, and of course he is a free babysitter.
He did prep all the food for the party but I suspect that was mostly because I told him point blank and almost blase do-whatever-you-like-dahhhling way that he would have to do it, as I was working so couldn't. He did ask me a couple of questions but basically I brushed it off saying he would have to, you know, use his brain, and work it out himself. (Funnily enough he managed it with no problems at all.)
Needless to say I love him too, but honestly I don't know what to do with him sometimes. I didn't work when the kids were little (although did voluntary work when I could), but planned to work when they were at school, and was also trying to build up some self-employed work whilst being a full-time mum. 6 months before the youngest started school, DH lost his job (sort of intentionally got fired - long story but his fault) and we decided that I would have a go at working instead of him as I was going nuts being 'stuck at home', but with the proviso that he would find work once they all were at school.
He later said he just couldn't do 'brainless' work and therefore chances of getting a job were practically nil. (Well, yeah, if you don't even look...) But refused to go on any training courses. Refused to do anything else to better himself. Refuses to apply for most jobs I find for him. (Why do I do this?) I have since found a course that he actually showed interest in - that he doesn't think is utter shite (miracle!) - which he is going to start in Oct. Of course, despite it being only 1 day a week I'm sure he's not intending to find any other work in the meantime or even when it starts.