Christmas is always a time for me when emotions come to a head. It's such a hard time when you've lost someone close, as it recalls all those memories. I'm so sorry to hear you've lost your dad recently and it is totally understandable if that is making you feel things more intensely and want to capture magic and feel the importance of traditions more keenly.
Could you sit down with your DH and just share your feelings, all of them. Not about the garland too specifically, which I think is a symbolic object here - it's something that literally connects you to your past, to your family members and so on, it represents a weaving together of all those generations and relationships - but about what Christmas means to you, what you want it to mean for you as a family, and why these rituals mean so much to you. It might be a good exercise to sit and try to think this all through on your own, and really understand the root of your feelings.
Once you have gathered them and you can take them to him, I hope he can enter into that emotional space with you. It could be an opportunity to ask him how HE feels about Christmas, how he wants to feel about it, etc.
One of the hardest things about Christmas, I find, is that it's a time when we have a sense of being dictated to by society how we should feel. We should be jolly, feel festive! It's a sort of "off the peg" emotional state that quite often doesn't actually "fit" us properly, depending where we are in our lives. That often prevents us from accessing what we are ACTUALLY feeling in the moment, from checking in with our actual emotions, and from feeling able to express them.
Perhaps then he could find it in himself to do things which might not come naturally to him, or be part of his traditions, for your sake, but you can also do it from a position of understanding his emotional landscape.