Tricky one, OP,
Can well understand how your good intentions to strengthen bonds between your DC and MIL (incl the 4hr travel) might start to feel unappreciated, if you're all made to feel too inhibited and on edge. Not very nice for you or her.
If PPs' suggestions (more frequent visits to you instead, or basing yourselves at local b&b etc.) aren't viable, it'd be a terrible shame to miss out on good times together due to both sides developing simmering resentment.
You've not said otherwise, so I'm assuming your MIL's generally fair? Do you feel she'd meet you half way on working out a compromise?
E.g. Yes to her DGC always wearing slipper socks inside, no shouting or wrestling competitions at Granny's, and that you'll ensure loud letting-off-steam play sessions stay outside at the park, but yes to her also accepting that your 2 younger ones' ability to self-regulate volume is limited(!), that it's natural for them to be active and exploring, and that if it occasionally gets too much for her, even once you've taken every reasonable step to prevent such, might she enjoy an hour's respite in her bedroom with a good book and ear plugs? Or a short walk alone?
Agree with PPs that there's quite a disparity between her normal routine as single older lady, quieter lifestyle, conscious of thin walls/ neighbours (who might have complained), versus 3 young children's perfectly natural (but unfamiliar to her) chaos and exuberance!
On a practical note, perhaps it's also a matter of re-framing it in the kids' minds: rather than the idea that Granny's no fun and stops us from playing (which I imagine would hurt her deeply), why not instead make a big deal out of enjoying special quiet toys and activities, which Granny loves (and will no doubt join in with?) during a visit?
Softer, less noisy versions that won't clatter and echo throughout:
bubabloon.co.uk/products/bubabloon-colour-in-with-washable-markers (no worry about choking hazard for the baby, either, as it keeps any burst pieces safely within).
Interactive, quiet fabric books. Another example here (As sophisticated or as simple as each DC requires. There are some brilliant ones to buy, though many are Hellishly expensive...but good project for making, if you/ an obliging friend enjoy crafts.
Even better if MIL herself is handy with a needle, and keen to help?
She'd then feel she's directly encouraging the end result of occupied, 'quieter' DGC, and they'd have a wonderful, personalised, hand-sewn gift from Granny. Win-win).
I Spy bags are a great distraction for over 3s . Easily bought, or good DIY step-by-step here
Foam jigsaw pieces for the floor will absorb noise. And good old Aquadoodle mats are always a mess-free activity standby! Storage space minimal, so MIL could stash both of them under a bed between visits?
Good luck 