I also support the decision for you and your mother declining the invitation. First reason is that, based on the background you've provided, it appears that nothing you do will bring you into better standing with your extended family. So why spend money you don't have to try to please people who don't think highly of you anyway? My second reason does not seem to have been discussed yet but should be considered. I'm not sure it's a wise idea for your extended family to expose your dying Great Aunt to a full-on holiday celebration with many attendees if she is supposedly in such a fragile state. You could make a good case for wanting to spend some quiet, quality time with her on another day when it would be less stressful for her (and for you and your mother). But even if the second reason is valid, be careful how you word it to others as it could be taken as accusing your extended family of hastening your great aunt's demise.