There are several tests for "older mothers" (over 35) in North America, starting from NT scan, to CVS or amniocentesis - if a woman wants to know about any future problems like trisomy, in the developing fetus. Are these in Ireland? A mother who knows months before labor date that her child will have Downs, at least has time to prepare mentally.
Sure, you can carry another baby - the proof is 6 months old
I'm 45, and've been thinking on and off if I could add to our family. My kids are 4 and 5 years old. It is great to have two children close in age - they play with each other a lot, all the while learning co-operation. I think largely because of this "training', my kids are doing great socially, in school.
Good luck with your decision!