Lighting the fire from the sun
It's the shortest day, with the sun the lowest in the sky, and thus the weakest. But still, to welcome back the light, we decided to try to light a fire from the sun using a Fresnel lens. Ours is more than a foot across, made of lightweight plastic. It works very well if it's a bright day, even in late afternoon. Then, using the lens, we burn the year into a piece of wood, and the words "happy solstice" into other pieces of wood, and prop them on the front steps. Important safety precaution: wear dark sunglasses, sometimes multiple pairs one atop the other, and do not permit anyone to stare at the very bright spot of light.
To maximize the chance of the spark succeeding in lighting a flame, we've been creating char cloth (Google it), which burns hot without flame, and then we put some other tinder around it (lots of experimentation here; recently we've been using shaved bits of "fat wood"), and blow on it to get flame. Someone stands by with a candle to capture the flame, and then we use that to light more candles and start a fire in the fireplace. We keep the fire burning all the rest of the day. Then it's time to open presents.
There are sometimes issues with it being too windy, although you can kind of do it indoors through a window, if you don't mind a little smoke. Sometimes we have to leave the doors and windows open to exhaust the smoke afterwards. Of course, sometimes it's cloudy. So then we try to do other things (besides a match). We have had success with a fire piston. We have had failure with a fire bow. We have also had failure with the fire piston. Then to get the year plaque we sometimes do "make-up solstice" when conditions are right. We've been pretty lucky with weather, and mostly do get to light the fire from the sun on the actual solstice.
For food, we start with pancakes in the shape of the sun (that would be... round). It took a while before we figured out what dinner food would be festive and acceptable to kids. We tried homemade pizza (again in the shape of the sun), but it turned out that the kids liked store-bought pizza better, and adults just didn't think that was festive. We finally hit upon cheese fondue for dinner and chocolate fondue for dessert, with various kid-friendly and adult-friendly dipping options. Fondue has the additional thematic advantage that it is kept warm by flame. Another thematic dinner we've done in the past is to barbecue, and it's quite fun to do this in the snow, because you leave behind a perfect circle of melted area.
Lighting the fire from the sun
Fire bow attempt