Of course the 10yo can play with his siblings, he dosnt get to do his own thing all the time when he is part of a family, my 10yo played games with their 3yo sibling it’s called being part of a family.
There are plenty of games and crafts to be played with without an adult helping too much which is what I said, colouring, children can use glue sticks and stickers with very little help, I get given sheets of paper with drawings, colourings stickers, cut out pictures on daily my youngest makes for me on her own, granted she’s now 7 but she’s been doing it for years. My most recent thing I’ve done to occupy her without adult supervision is give her multiple sheets of sticky gems and told her what’s she’s allowed to bling, she’s very kindly blinded my walking stick for me, she’s loved it. Her older siblings asked for some more so they could bling their own things. The craft items can be set out each day, all exactly the same so no “best” or favourite item, all get the same stuff to use.
The kids can play hide and seek, the floor is lava, create a play or dance show to put on when the parents are home. It’s just a matter of planning and getting creative.
Sit the children down, tell them going forward they are going to be able to do things, they can make a card for someone they care about, draw a picture, make a collage just no paint and glitter, they will get rewards points for helping, getting involved, cleaning up. Write the name of activities on paper and get each one to draw from a hat, they get 1 each and that’s their activitie that day, all 4 do it and all 4 do the game/activities, they each get a reward treat when your home. Or you can say ok, when I’m at work tomorrow I want you to pick one craft, 1 game, 1 board game and 1 other thing each to do together throughout the day, one after breakfast, one after lunch and 2 in the afternoon. Buy a bag of sweets, treats, prizes from home bargains as rewards or for every time they participate they get 50p each to spend at the weekend.
There is obviously something going on with the 8 yo but you can still try getting her to partake, she might just like the structure.
One thing I did in covid when we had months of finding things to do, was get them to go through the house finding certain things/toys, one day I asked them to find everything dog related, they collected all dog related toys in the house and counted them. I then sent them in a mission to find everything LOL related LOL doll and accessory, they spent an entire day looking, dressing up and organising they all, same with shopkins and so on. We set up a jungle using house plants and soft toys took pictures, moved them around like we were David Attenborough watching real animals, this could be done outside if you don’t have house plants, maybe turn it into the kids work together to make their own video..
They can also do what my DCs have done all day today, zone out on tablets for the day, watched their videos and played Roblox, no one was up to doing anything today so other than a my youngest riding her bike to the shop with DH it’s been a day of tablets and phones, and that’s ok!