God Squirrel, I am really shocked at your DP's attitude. It's well known that death makes many people feel "awkward" around those who've been bereaved, 'cos they're scared of saying the "wrong thing" or because they don't know "what to say" .... and this can therefore lead to bereaved people effectively being "avoided", even if no hurt is intended. However, people who feel awkward do usually realise that you don't make snidey, critical remarks to someone who's grieving - you don't belittle their loss & feelings (i.e. "being all miserable) by comparing it to their own so-called stoicism in coping with a cold marvellously !!
I have to say that remark was tactless and insensitive in the extreme. Like, a cold is what's really bugging you right now, the stupid bloody idiot. Sorry, but even the thickest individual would surely realise a comment like that would hurt in your current circumstances and it's beyond me why he was so cruel. And the lack of hugs is quite astonishing too .... going back to the not knowing what to say theory, a bit of affection could effectively say it for you couldn't it ?
I've a nasty feeling (obviously, I don't know you or him, so am just guessing by reading between the lines) that your DP may be sulking because his kids have gone home and he sees it as "down to you". Okay .... I can understand he'd be disappointed if he'd been looking forward to having them stay but really, I do think the death of a very close and loved relative should take priority, when you take into consideration that it's unfair to expect you to put a brave face on (if you don't want to and/or don't feel up to it) and you also need to spend some time with your own son who will be similarly devastated. There are very few occasions when the feelings/wishes of a responsible step-parent are given priority over stepkids & contact with their absent parent - and rightly so - but I maintain this sort of occurence is one of them. Obviously, you're not asking them to stay away for ever - and whilst you won't have "come to terms" (or anything approaching it probably) the next time the skids come to stay, you will be able to face them a little better equipped emotionally as the initial, gobsmacking, knocked you for 6 shock of your Grandad dying is likely to have lessened a little.
Hope I haven't said anything to offend you, but I bet that has something to do with his nastiness. There have only ever been 1 or 2 times when my skids were "disrupted" (not ignored) - due to me being in hospital re: miscarriage, and due to our baby being ill and us taking her to emergency doctor. Whilst DP was not horrible about it, it was clear that he was still terribly worried about the "effect" on skids, to the extent that, even though DD had severe gastro-enteritis, he went and got skids a day late (this was even though doctor had said it was potentially contagious. BM was told and still wanted him to have them - so she could go out!). I felt very very annoyed he'd done this as I felt that to postpone seeing them a week would hardly be the end of the world and with a sick baby (literally) I did not want the extra work of 2 more noisy boisterous kids ... I just wanted to look after the baby in peace. I honestly feel that DP was more worried about bloody BM's reaction (she takes every opportunity to slate him as being a "bad" dad) than his own disappointment in delaying their visit.
Have gone off tangent a bit but I do wonder if he now regards you as having spoilt his time with skids - however illogical that is ? I do think though that many absent fathers can be very very touchy indeed on the issue of their children if they perceive that the skids are "unwanted" at any time. They jump to this conclusion even when the children are usually welcomed with open arms and it's dire circumstances which lead to a step-parent - shock horror - saying that actually, right now, just at this time only, you'd rather they weren't around. I think "guilt" has a lot do with that sort of reaction particularly and ironically, if they are a responsible loving parent, yet still get loads of grief from their ex which makes them doubt themself and terrified to "put a foot wrong".
Whatever the underlying reason for it (his lack of sympathy) though, it's completely unacceptable. I hope you have other friends and/or relatives close by with whom you can share a hug, or spend osme time chatting about your Grandad and how you feel.