Separate meaning from work
The heart of a tradition may be smaller than the routine built around it. A large meal may really be about gathering at one table. Elaborate decorating may be about displaying a few familiar objects. Hosting can move to another home while your parent still chooses the menu, tells the family story, lights a candle, or gives a toast. The meal could also move to a restaurant or be celebrated on a different day.
Ask before taking over. A change intended to help can feel like a loss if the person is not included in the decision. Offer choices about what to keep and find roles that match their energy and interests. The people whose votes count most are those most affected, which can include emotional, physical, and financial impacts.
Gifts from the heart
Gift-giving may need its own conversation. Your parents are probably trying to do what they used to do and still think is right, and their interest and success in doing that may vary. They may insist upon grandkids opening gifts a particular way, and that adult children must all give each other gifts. These both represent a veer from gifting and into performing of rituals. The best time to express a desire in how gift giving changes is long after one holiday and long before the next one. With no criticism of the past, ask or tell your parent how you'd like things to change going forward to align with the family members' holiday goals.
If your parent requests no gifts - and if you believe them - look for a small compromise. Give them something disposable that they can share with others. It's probably extra stuff that they don't want, not avoidance of having a nicely-wrapped gift to open. If it really is that they don't want anything shiny to open, consider if they'd like a gift received in private.
As for gifts from your parents, they may want help. My parents are grateful when I send Amazon links to gifts their grandkids would like. I also suggest what stores they could give gift cards to. I try to encourage all families have direct, 1-to-1 relationships, but I help those succeed through reminding them of each others' birthdays.
If someone helps with gift purchasing, they should keep records and follow your parents’ instructions. A helper should not use access to buy gifts for themself without involving a third person for accountability. Fraud is common in older adults, and setting boundaries will help both avoid fraud and avoid you worrying about it.
Make gatherings easier
Consider transportation, stairs, seating, hearing, lighting, temperature, rest, dietary needs, and the length and noise level of the gathering. Share the schedule in advance with the entire family including the time when things are set to end. All family members will appreciate it if you can set aside a quiet place where anyone can take a break, though you may find it ends up being an escape from something other than noise. If that is the case, investigate the root cause or create additional quiet escape rooms. A shorter visit, smaller group, video call, or celebration on a different day may also preserve connection better than insisting on the old format.
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Next step
Choose the traditions to carry forward.