I also use my main floor kitchen/dining room/great room for food prep and meals and arts and crafts. I have a play room in my basement with big toys and keep the noisy ones down there too. I have found that we spend more time upstairs than down because of the time spend with food prep and clean up.
I have quiet toys upstairs (puzzles, train, books, duplo, blocks, cars and trucks) plus my daughters bedroom is just off the great room so all her own big girls toys are in there. I sometimes bring up or rotate toys from the playroom to change things up. I also allow more physical activity in the playroom and expect upstairs play to be quieter and more focused based on the toys I have chosen for upstairs.
You will need to keep the kids in your sight when doing all food prep and clean up, and it does take longer than you might expect because there are always a lot of interruptions. They will also want to be close by you so I don't think it would work to expect them to play in a spare room while you are making food.
We clean up the toys a few times a day so the room is not a mess. But because my own children, 1 1/2 and 4 1/2 are always playing in the great room during non-daycare times, I am used to there being toys around. Just a part of life with little ones