All good ideas.. the bricks or rocks idea has been used for ages when in a horse drawn sleigh. Wrapping them with a blanket or old drapes allows you to rest your feet on them with getting burnt.
- I'd consider heating up some bricks and then placing them under peoples chairs to keep them warm
- If you really want to get sophisticated, I'd look into heat pipes or pumping heated liquid to the right places
- Heated outdoor mats for melting snow might work if placed under people's chairs
The fireplace with a hat, would work well for a wood stove fan.. and cooking steaks. Easy enough to make the hat if you steal a trash bin lid from a competing gated community, at the next pickle ball event.
Instead of heat pipes or heated mats, a bunch of high back, used car seats, with their ubiquitous heating elements would be great. Comfort and heating in one.
The power needed could also be used for a beer fridge.
As has been mentioned, moving further south would be most effective.
To that, I shall again mention that there is no snow in then OP image, and is reportedly in Arizona were my fellow northerners go to in winter to get warm.
I'd you put some ND, MN, SK, or MB dwellers in the photo like those 3 from Egan... They wouldn't need heat at all.