Manipulation and abuse, plain and simple ... You've been down this road before ... Don't allow them to dupe you again!

I'd spend the holiday (guilt and all) exactly as I wanted to ... At home with my partner and cats!

Politely decline both invitations by saying you appreciate the offer but already have other plans ... Don't elaborate any further, and if they try to get all snotty and argumentative with you about it, simply thank them for helping to prove your point, then calmly hang up the phone and refuse any further engagement with them as nothing good will come of it.

And, remember this ... The guilt you feel for not going will subside a lot quicker than the sting of any fresh wounds they bestow upon you if you do go!