51 should we go for another?

[AnnaSi]

We are currently debating whether to have another child.

Our child is 5, we had him when we were both 45, and we are both 51. I wanted another but my husband was one and done. Recently he's seriously regretting being OAD. Due to the fact that he can see our child would have really benefitted from a sibling due to his nature, and also we enjoy being parents and feel like we could manage another one.

As our first was a donor egg, we can theoretically. have another as there are embryos left and the clinic treats up to age 54. But are currently considering whether this is the right thing to do given our ages and possible pregnancy complications. It feels like a heart vs head decision and its difficult to come to a conclusion. Any advice would be gratefully received.

I have used a donor (sperm in this case) and have a 5 year gap although I was in my 20s when I did so cant comment on age (as you say that's a head over heart matter). However I can say the eldest was at school when I had twins and therefore was always at a different stage of life and at times (like presently late teenagers/young adult) they appear to have a respectful/look up to dc1 relationship but not necessarily a sibling relationship.
Also think about what happens if you have twins (obviously a higher chance) even in my 20s it took more out of my body (spent 3 months on bedrest) than the singleton. Obviously it costs more in childcare but I'm now bracing myself for the cost of university. In 19 years will you be able to fund one, maybe two through university?