Definitely out in the fresh air during the day, preferably afternoon.
In our house, DD also makes cookies in the afternoon - from scratch if we have the time and energy, or just "slice and bake" from a half batch that I have frozen earlier in December just in case...we are all in the kitchen peeling veg and making stuffing etc together.
We have a nice dinner that DD enjoys, and that marks the start of the slow down in our house.
We clear dishes away (and from mid-afternoon on 24th, everyone has a role in meals, young DC can carry things between rooms etc and help stack the dishwasher).
Then we go into the sitting room, with the lights lowered to just side lamps, and we light the Christmas Candle (to show that there is room for any weary travellers in our Inn). We have a few minutes talking about the year just finishing, remembering the good and bad about it and family members no longer with us to celebrate, (always finishing on some good things).
We pull out the cardboard box that is our hamper. It has always been known that I fill it, not any Elves etc. We all get new PJs, and everyone gets something nice for the bath/shower, and the makings of hot chocolate. I also put in DD's stocking, her plastic plate and glass with Santa on it from toddler-hood, the family edition of "Twas the Night Before Christmas" and her snowman covered hot water bottle.
She puts out her stocking, and the cookies (from the afternoon) and milk for Santa.
She goes up and enjoys a Lush festive bath-bomb enlivened warm bath. Where she can relax as long as she likes, and the bath toys are available if wanted. She gets into her fresh cosy new PJs and comes back downstairs for her hot choc snuggled up on the couch.
Then we both go upstairs with her snuggly HWB, where I read the book, and maybe another story or 2 when she was younger (nowadays, I turn on the audiobooks or Radio 4 comedies on her ipad - but she still wants TTNBC to start with!). Bedtime stories have always been a part of bedtime in our house. I keep the lights low in her room too - not the bright main light, just the bedside lamp. And keep the chat low too - lower voices, general chat, not getting worked up about it all, and not giving out but more gently coaxing along. The tv is on during the day, but switched off when we start dinner (and doesn't go back on until she's in bed) - we'll have the radio on part of the time in the background, but not very loudly. So it is all very calm and measured.
DD is a demon for sleeping, always has been (she has been on melatonin for quite a few years) but Christmas Eve is normally one of the few nights where we can get her to bed relatively calmly and know she will sleep.