Good grief Annge so you're an ambulatory wheelchair user who can't use your wheelchair in your D's house, so have to struggle with using sticks and pain, and you're being castigated for not being a mind reader, knowing that your D needed help without her asking for it, despite having provided 4 days of child care for her first child!!!
I'm pleased that you've posted again and although I'll be criticised for saying so being an EP myself, but hey ho I'm used to it, the brief history you've given of your relationship with your son and his wife came as no surprise. I suspected there was some kind of past disagreement which is why they appear to have taken this opportunity to break all contact with you.
TBF Casdon, this isn't about your relationship with your D, it's about the OP's relationship with her's and if you had missed a subliminal message from your D that she was struggling to cope with a new born and toddler and needed your help, would you have expected her to criticise you to her sibling(s) and wider family, or perhaps realising that you hadn't picked up on it, simply asked you.
I do hope Angee that you'll have realised from the vast majority of responses you have received that you are not at fault here. Any fault lies with your daughter, your son, your d.i.l. and any family member who is unable or unwilling to call out the terrible way you're being treated.
Be strong and take care of you.