I call chili with beans in it Chili With Beans. Chili is a type of stew. Chili with beans in it, also a type of stew.
As for the task at hand, my step-grandmother would make both a pot of chili AND a pot of beans at family get togethers sometimes. Provide a slotted spoon and they can throw their beans in the chili if they want.
As for the heat issue, maybe mash up or blend up some chilies, fresh or cooked, and have a good sized bowl of it on the side for people to thrown a spoonful in their chili/chili with the beans if they want to spice it up a bit. Maybe roast some serranos and get those chopped up/blended up on the side. One of my favs is a bunch of chile pequins mashed up in the molcajete with just a bit of liquid to spread it out and help lube things up for better mashing (maybe just a bit of water, or a bit of tomato juice). You throw that in a stew or soup (chili in this case) and man, it'd be good for a quick heat. Obviously a lot of work, both making it and just finding that many pequins.
OR maybe just a bottle of Louisiana hot sauce or other type of pepper sauce to pass around/on the counter.