It’s the “doing” that counts, not the completion! Anything that stimulates memory, senses, and sense of wellbeing, rather than being too task-orientated, tends to be easier ime!
I would bring in some kit (do you have a small budget for supplies?), set up, tell people what you’re doing, and invite them to have a go. Take items round to those who can’t come to you.
Music (playlist for life have some great resources) - we have a “musical memory bump” ages 10-17 so nearly everyone will remember some tunes from this time in their life. Get a playlist together from each person if you can, to share - ask family members for suggestions of songs if necessary, perhaps run a quiz for those who can, guest performers, having a go with percussion or instruments from other countries, have a day themed around a decade or a country…
reminiscense - there are some lovely books (Robert Opie?), the BBC archives website if you can get it up
on a laptop is fantastic to get a conversation going, local history websites too, bring in old photographs, old tv programmes , historical events, old newspaper cuttings etc, find out a bit about people’s life histories and which bits they enjoy sharing if possible.
sensory activities - scents, lights, textures - loads of ideas online - look at Alzheimer’s Society online shop, loads of lovely things. Clay modelling, Lego, magnets, (magformers), twiddlemuffs, fabric collage etc can all be really enjoyable for people with cognitive loss as it’s something you “do in the moment” which is generally easier than something that appears like a “task”.
Simple cookery (nearly everyone can enjoy the smell and touch of baking bread, for example, at any level of memory loss)
indoor gardening - flower arranging, simple seed planting, can be really joyful, enjoy the smells and textures…
Hand massage, relaxation exercises (can be really really simple like gentle music and a meditation or simple breathing exercise to music), very gentle exercise (I know of one place that does a “tea party tunes and toe tapping” afternoon)
simple games will work for some - tiddlywinks, snakes and ladders, hangman etc.
and yes sometimes just start doing it, rather than asking too much, don’t be afraid to be the person who looks a bit silly to put others at ease and enjoy!