OP, I'm sorry it's so tough! I have college aged kids now (and oh how I wish the house was bigger!), but we did homeschool K-12 (no screens until teenagers, low screen use at that point).
These are the things I would do (many of which I am putting into place because I'm also pandemic exhausted):
1) Block out time daily and weekly for your own mental health, and make it a priority. Your partner and kids have to respect the time, period.
2) Pull your kids out of school so you can homeschool/unschool. I suppose this might not work if your older child has an IEP, but I truly believe most children will be better served this fall by being homeschooled than attempting distance learning, even with parents working FT (or maybe especially with working parents compared to the nightmare of trying to manage distance learning during work hours). Minnesota is a moderate regulation state in terms of homeschooling, but parents are automatically designated "qualified to teach".
3) Maybe switch off days WFH with partner, so you each get some days in the office for work time with fewer distractions.
4) Invest in audiobooks for your kids. Or borrow audiobooks from the library. Teach your kids to observe a quiet time everyday, with audiobooks an allowable activity during this time.
5) I'm sure you must have indoor recreation activities for your climate, but maybe you can add more? Maybe a ping pong table in the basement? A yoga swing? Hand weights?
6) Be sure to have many options for quiet occupation, then rotate them rather than having them all available at once. Lego, other building blocks (mine loved Keva Planks), castle blocks, Playmobil, Rokenbok, air dry clay, watercolors, magic kits, Etch-a-Sketch, yo-yos, knitting, other handwork, drawing materials, paper airplanes, etc. For some kids an electric keyboard with headphones is a nice occupation.
7) Continue to budget for things that make your life easier, such as the meal kits, some child care, etc. Prioritize spending on things that increase your available time and make you happier. For me, I'd rather have takeout than a meal kit I have to cook and then clean up from. We hire out the lawn care.
8) Create a strong rhythm for your days, weeks, months. Children thrive on rhythm and routine (so do adults, but we're more flexible), and it's one thing Covid has taken from most of them. Family meals together, family movie night once a week, family game night, seasonal observances, religious observances, fun observances -- all things you can use to help the days feel separate. Heck, we have a rotating weekly meal plan to help us know what day it is (something we did when they were young and brought back in Covid). Today is National Dog Day, so we got the dogs a new toy to play with (and for us to play with them with). In September we have family observances for Holy Cross Day, the Feast of St. Matthew, the autumnal equinox, and Michelmas.
9) Social interaction is just going to be hard! Maybe weekly Zoom visits with friends or family? Maybe start old-fashioned letter writing and send cards and small gifts (stickers?). I know there are some websites out there where you can play a board game together virtually.
10) Create opportunities for your children to contribute to running the home, which can help you and make them feel good about themselves. At that age my kids were vacuuming, making beds, folding laundry, etc. Some 10 years olds can cook a simple dinner. The point is, give them things that build confidence.
The screen break is a fantastic idea! We were never big on screen use, but I do know many families who cut it out and found life much better (after the transition). I would add in -- for their ages -- not watching or listening to the news constantly in their presence. Things are tough enough and more information doesn't make it better for children (or for adults, really) -- it increases anxiety. I'm not saying they should have full shielding at their age, but I would choose to be the filter for any news information they get. I would also focus on educational TV when they are allowed to watch -- programs like Nova, Nature, etc. Not that they can't ever watch anything fun -- that's what family movie night is for.
Good luck!