Crikey they're hardly crimes of the century!!
constantly buys DS new things pretty much gets something every other week, new toy, book, dvd. But not DS2 who MIL doesnt have once a week as goes to nursery - fine just take them off him when he gets home or make the point in front of MIL that 'you have to share this with DS2'
have decorated a new bedroom for DS, filled with toys, his school photos and a drawer full of clothes 'just in case; - So what, they're not going to end up living there no matter how much she might like that - let her waste spend her money how she wants
We bought a tent, they are now 'talking' about buying one too - hmm tricky, my DSis's FIL camped near them last year, this year he's staying in the same villa. Proceed with care!!!
when DS was in nursery pre-school we had issues with his potty training and he got better whilst at nursery so for 1 WEEK only we put him in for the full week (so MIL didnt have him that week) and we had tears to DH 'I knew this would happen and you'd stop me having him - it's over now, let it go. Nothing came of it.
Let themselves into our house to use our facilities whilst we were away for the night as they had a power cut without checking in advance (we were only local) - get your keys back, if it bothers you that much do not enable this behaviour.
Xmas and birthdays they ask what DS would like (yes great they ask) then buy that and at least 2/3 things on top and its always the biggest present - what about your other child?
Whenever DH mention he is taking a days leave in school holidays MIL always say dont worry I can have him. DH does say he actually would like to take the day off to spend with his sons - she's trying to help, the number of threads on here about GPs not offering to help...
When my mum is visiting MIL used to pop round while I was at work unannounced for a coffee with my mum - what a bitch. Seriously, she was maybe trying to be nice.
I do get it. I have zero relationship with my FIL but he is only interested in himself. BiL would be round ours all the time if we let him. You've lost this on one and you will look like a pratt if you make a fuss, just be more circumspect in the future. Like i think BiL would like to come on holiday with us. We never offer/mention it so it's not going to happen.