I am an older mother and I understand your situation, and am sorry for the blunt way some people respond to posts like this. I think despite everything I probably wouldn’t do this at 53, especially with no partner or family support.
That said..
If I understand right you are considering donor eggs/sperm or donor embryo?
I think this is right because at your age the chances of pregnancy using your own eggs are close to zero and possibly in fact zero. You could have some investigations or advice about attempting with your own eggs but I am not aware of anywhere in this country that would offer that option, and I think it would be very time consuming and overwhelmingly likely to fail. You don’t have time, so unless its own eggs or nothing, I would accept the donor route.
I think, and would advise clarifying with a specialist …In the absence of certain medical conditions, if a woman uses donor eggs, then the chance of a successful outcome and carrying to term are based on the age of the egg donor, not the gestational carrier. The same applies to disabilities related to maternal or paternal age. It will be based on the donors, not you. So to clarify, if the donors are both aged 25, your chance of carrying to term, and the chance of the child having a disability, will be the same as for a 25 year old woman. It isn’t quite that simple as age may make you more prone to certain conditions affected pregnancy eg gestational diabetes, but it’s a guide.