How am I supposed to spend a whole day with my kids...

Do you have stuff to bake? My kiddo loves baking with me! You could also try crafts or dance parties

My boys are almost 3, and 10 months. The baby is easy. My toddler loves to take his cars and run under/between my legs like I'm a tunnel. I turn it into a game by moving around so he has to change direction. Also, balloons. We hit it back and forth almost like volleyball, and it keeps him entertained for an hour straight. If you can, maybe make some kinetic sand and put it in a bowl or small tote so they can fill small cups, or run little trucks through it. Hope these ideas help!

Messy play, dance parties, forts, toddler yoga on YouTube, baking/ cooking, glowstick bubble baths, painting, puzzles, hide & seek, building, wrap puzzle pieces in tissue paper, colouring, draw out shapes on paper and then on post it notes and hide them, board games, kinetic sand, play doh, cleaning, water play, pouring activities

Activities.

Hey, there's a channel on YouTube called Hapa Family and the woman that runs it has a series called Montessori at Home. Within that she has done a lot of videos of activities to do with your [insert age here] child which may give you some ideas for each of your children, and also a lot of videos that explain how to effectively 'discipline' your child which I've found so so useful.

Do you have a garage? Sometimes, you just need a change of scenery. If you have cars in there, let them play "driving" or just crawl around between the seats. If not, open up a random box or 2 and let them each choose a treasure to bring back in the house when they've explored long enough. Bring a water table inside to an area with hard floors. (Put down 2-3 beach towels) bring some snow inside and let them play with it until it melts (pretty quick). Then they can splash around for a while. Add some bath toys or let some of their characters figures have a blizzard beach party. You can throw it back on the porch when you're done. Let them go through your closet and walk around in all your old shoes. Use bubble bath to lengthen bathtime. Get a long roll of paper and tape it down your whole hallway, or living room floor of you aren't that brave, haha. Let them go crazy with crayons and markers. Make outlines of everyone and hang them up. Include the date so you can see how they've grown in a few months.

Shred paper and let them throw around the paper confetti. (Blizzard!)They will love how messy it is. Keep it all in one room for clean-up purposes. Let them crack all the eggs for scrambled eggs. Move furniture and build a truly magnificent fort.

My son loves cooking and baking w me

You have to teach your kids how to be board. They won't use their imaginations unless you give them the chance to. You do that by having times with no TV or devices. You only offer healthy stuff. And don't use candy as bribes. But more of a treat without them knowing it's coming. And not every day. You also have to get down and off your own phone if you use it often, and start playing like you're them. If they aren't playing with you and the toys you choose, make it look fun.

Transitioning away from screens will always be hard, but they’ll get used to it. Instead of offering fun/simple activities as a choice, inform them “it’s time to color! Do you want crayons or markers?” Etc. Id they ask for screens, say we will not do screens until after dinner (or whatever your desired boundary is). They will have a tantrum, but they will get over it. The most consistent you are in enforcing rules, the more they will accept the rules. Keeping the a consistent routine each day will also help

Create a loose routine. Get rid of the candy. Getting rid of screen time until the can play freely & happily without it for at least a month. From there, you can reconsider bringing it back on a set structured schedule. Read books, have dance parties, set up obstacle courses. Put away most of the toys & only keep out a few things. Then after a week swap everything out. Join the 1000 hours outside challenge Facebook group & for the holidays consider investing in quality cold weather gear.