Well you there's your answer: you care; he doesn't.
He doesn't care about you, or your son, or what his family think of him. And he doesn't have to because the more you do, the less he has to bother. But you have created quite a rod for your own back.
By wanting to create a perfect (or near perfect) experience you've raised the expectations for everyone. His family now expect thoughtful gifts, hospitality, nice food - what was it like before you were on the scene, did he bother with getting presents then or was it some last minute token thing? Did he invite them round to a clean house or was it a 6 pack of beer and take away pizza in front of the telly? Or was he the son at home, and never had to bother because his Mum took care of everything?
Similarly, you are raising your dc with standards that align with your own about what makes a happy Christmas. What would happen if you set the bar slightly lower? Whatever 'traditions' you set are what they will become. My dc1 doesn't do 'elf' but always has exciting advent things; my dc2 has 'elf' as the pinnicle of the build up; dc3 is married to someone from a different faith background. So far my dgc all cope with whatever is in their own home.
Bottom line: is DH the same in all other aspects of your life. throughout the rest of the year? Is he similarly uncaring, is he happy to take on all the thinking and the work? Or is it just that he's not so bothered about the Christmas magic?
If it's just Christmas then you have to decide whether you effectively do it solo, because it is so important to you (although sad that he won't recognise the importance to you and pull his weight just becuse of that), or whether you can compromise on what it might look like - e.g. doing secret santa for family (or not doing presents for them at all [by agreement]).
If DH is as lazy, or unbothered the rest of the year - well that's a big question for you...