Definitely does look like a bomb went off, but don't lose heart! The first thing I'd go about doing would be to get those branches and fallen trees cleared up. You could either rent a woodchipper and chainsaws and do this yourself, or you could hire a
tree and brush removal or lot clearing company to get it done for you. Chippers usually rent out at about $600/day, so that might be something you'll want to consider depending on your budget (obviously depending on the manpower you have available that'll be cheaper than hiring a contractor). You said you have family who might share it? Maybe split the cost with them, or get those bored teenage nephews up to the place for a few days of gettin' grubby running the chipper lol. Stumps can be removed by a determined individual with an excavator (again, I'd try renting a small one for starters or just asking your neighbors). You certainly don't
need to get rid of them but if they are left to rot in the ground you'll wind up with big holes everywhere eventually... If it's all clay, grading and leveling might require someone with a dozer or grader to smooth things out. I'd even look at drainage ditching to ensure you won't get ponds in the low spots when it rains.
Starting a good pasture on the clay will probably require getting several tons of good topsoil brought in. You could supplement this with a little mulch from the woodchips you've ground up. Throw down grass seed, timothy, alfalfa, chicory maybe and spread hay over it to give it some nutrients to chew on. Add some fertilizer for a jumpstart, and start compost piles for the future with whatever food scraps, hay, leaves, and grass clippings you can get your hands on. If you're doing this all this spring, you might line up nicely for warmer weather to make things really take off!
Additional aesthetics? Get some boundary
fencing billings in, plant some trees for your livestock to relax under and depending on your water situation look into getting good water lines plumbed into the ground. Clean water vs. dirty makes a 20% difference in weight gains, with cattle at least (source; worked an Australian cattle ranch for a few years, my boss was incredibly detail oriented). Land you don't touch will grow wild, but might sprout a ton of "repair plants" like brambles, blackberries, briars and such which will need containing to allow grass to eventually win the race for sunlight. Could take years, depending on how much you actually leave it alone when it comes to planting trees etc.
Cost? A lot if you hire people, like at least $40,000. That's not helpful I know lol, again, I'd suggest just doing what you can by yourself when possible to save money.
You're not crazy, but know yourself and your abilities/budget/goals for the property before you get too deep into the project. Nothing wrong with moving slowly with it and seeing how it recovers on it's own.
