This must be terribly stressful for you, because you like to have everything sorted well in advance but, you're going to have to let him take care of it this year and perhaps he won't mind running around last minute when the shops are busy and the shelves are empty, you would be surprised how many men seem to enjoy shopping this way.
I work in retail, and December 23rd was always the busiest day at the grocery store which usually was women doing a frantic last minute shop, and December 23rd was always the busiest day at the retail store, with men doing a last minute shop.
I can understand buying the groceries last minute because you want everything to be fresh and all those vegetables and meat and everything else takes up a lot of room in your fridge so you don't want to buy too far in advance...
But the buying of all the presents and decorations and everything else, 36 hours before christmas, that never made sense to me. It seemed like a really good way to not find what you were looking for, and have to spend more time in line but, he was almost all men shoppers doing this and they didn't seem to be too bothered by it.
If you really feel you need to, then contact the family and just remind them that they need to talk to your husband because he's decided to do their shopping this year (well, that's a bit of a stretch, it's more that you've decided that you're not doing it but, same thing...) so if they don't get presents or if the presents are extremely unthoughtful, they'll know who was responsible.
And if you have a feeling that you really know what they would like and you see something that's just lovely for them, you could consider getting it, keeping it separate, waiting until your husband more than likely drops the ball on getting them a good present, and then later, quietly, in the hallway or the spare bedroom or something, give them the other present and just say, I wanted to get you something that I thought you'd enjoy...
Or not. It's up to you.