First off are you a planner or a "go with the flow" person? I'm the former so I need a plan or I'm more stressed! And secondly, delegate - honestly you're the host not the slave find a couple of trusted people who can help.
So for me, in advance I'd plan
Music in background - loud enough to fill gaps, but not so loud people need to shout.
Drinks table/trolley - mix of alcohol and nice non-alcoholic drinks (splash out on some of latter especially if so many aren't drinking)
What happens after dinner - game, movie, sitting round chatting? Decide before and get it organised so there's no "oh I don't mind, no you choose, I don't know what would you like to do"
Most importantly make DH 100% in charge of these three things - be really clear on this point, he finds Spotify lists, organises and tops up drinks plus extras like ice and lemons etc and on the day makes sure it's all flowing.
Cooking
Simplify - pick a starter and dessert that needs minimal prep or forgo starter and just do nibbles as aperitif then the table is just set for mains
Main course what can you do in advance - can anyone join or help? Someone you like, trust and are happy to have in the kitchen? If not DH is also responsible for keeping folk out of your way
Clearing up - everyone dives in - unless you're obsessive about your dishwasher stacking, then everyone clears, scraps and rinses and you stack.
Dressing - layers, layers, layers. Personally I feel stressed when I'm hot, I get hot when I'm stressed 🥵
Kids in their room, no big deal. Depending on age and what you do post dinner ask them to stay for a bit then they can head off. Grandparent with dementia can someone help out keeping an eye on them?
And if you're not a planner, ignore all of that and go with the flow!