Is this reverse? I can't understand how anyone can't sit and reflect on the situations given in the OP, and realise they're causing a young family undue stress.
Seriously OP, you can't just text to say 'taking little Jonny out for lunch, back later' when lunch has already been catered for at home. Surely before taking your grandson out you'd say something along the lines of "I'd really like to take Jonny out for lunch whilst I'm here, is there a day that would work for you?".
Kids throw their bedding off, they get cold, they wake up. Again quick cuddle and back into bed. You could give your grandson the 'gro-to-bed' sleep sets, They are a duvet which zips to the bottom sheet, stops the duvet being kicked off, also prevents risk of suffocation, as you can't get tangled up in the bedding, and stops falling out of bed.
You need to take a step back, next time you go and stay, ask how you can help, ask if you can take one or both kids out to do X, Y and Z. Don't criticise your DiL or you ds, you may not agree with their parenting, but it works for them, so keep schtum!
These were the things that my mil used to do, and honestly it would do my loaf in:
Change the kids clothes, because she didn't like dd in leggings so she'd put her in party frocks (dresses are totally impractical, especially so, when learning to go from crawling to walking).
Change ds out of soft comfy clothes into fussy clothing like a sailors outfit with very unforgiving fabrics.
Put make up on dd when she was 3!
Give them sugary shit every time we went to visit or she'd come to stay.
Bring endless plastic tat and bags of clothing, I know it was meant well , so I'd always thank her, but we live in a tiny house, and just didn't have the space for it. Funnily enough it did dh in more than me, but he could never say 'no' to her, and so he pretty much stopped inviting her over (I'm sure she held me responsible for this).
She used to demand constant cuddles and attention from the kids.
What I would have loved:
Taking the kids out for country side walks (we live rurally with lots of lovely walks from our back door).
Playing quiet games with them like bingo, (kids would have loved the attention and it's really good practice for turn taking and listening skills) read them stories, and taught them a few songs (mil was a really good singer).
To do some messy play with them, clearing up straight after instead of leaving me to do it, adding more to my work load
Given them fresh fruit / veg, prepped and cut up.
To ask us to stay, and ask dh to help with meal prep and clearing away, not expect me to do it all whilst trying to juggle looking after the kids...in fact I would have loved it, if she and dh cleared away as 1) they could chat whilst being industrious and 2) I could have had time with dc! Instead I'd be the one clearing away, whilst they would be chatting in the living room, telling the kids to pipe down, so they could chat 🤯, or ushering the kids into the kitchen for me to look after!
To not bring toys (except Christmas/ birthday and then not go overboard)
To not change their clothes, unless they were wet, they are not dolls to be played with
To not put make up on dd or squirt perfume over her.
To not give them junk food, and particularly not before lunch!
To not make 'helpful' comments aka criticise my parenting.
To not constantly tell me how lucky I am to have married her son!
To not demand attention from the kids and demand kisses and cuddles, of course if the kids went to her for affection, that's totally different, but it should always be on a child's own terms not on an adults.
And what I really wanted, was her acceptance of me as an individual, not as a wife or grandchild giver. She could have had a fantastic relationship with me, I'm easy going, genuinely like people, and looked after her when she had a bad fall resulting in a hip replacement. But she made it so hard, after we had kids, that in the end I left dh to do all the inviting / visiting, as a result we seldom saw her. She died a few years ago, the dc never really knew her, which was a shame, it could have been so different, but there we go, we make our choices for better or worse.