Has your mum expressly said she doesn't want your partner's parents to come? Or have you made that determination yourself?
If the former then you are on solid ground, you can't really compromise with your mum being comfortable or not in her own home.
If it's the latter then I see why you are coming in for flak.
I'd have them both round here so that's not the issue. We could easily accommodate everyone. I've not mentioned it to my mum as simply put i know and understand her problems and if I put this on her she'd likely suffer an anxiety attack.