I can't comment on chances etc BUT i can tell you what it is like to live with down syndrome.
When I was 20 weeks pregnant the ultrasound picked up a heart defect in dd1 which turned out to be very serious but repairable. After having a fetal cardiac scan - we were told if dd1 was born without down syndrome it would be very very rare indeed. ( we have since learnt that our chance at that stage was about 1 in 2) We declined further testing even though it would have been with Prof Nicholaides at Harris Birthright Trust. ( the man to have if having an amnio/cvs)
Our dd1 was born with down syndrome. At 8 weeks old and 8lb soaking wet - she underwent two open heart surgeries. After three weeks in London post surgery we went home. She now is a healthy almost 6 yo - in terms of her heart defect - if you can't see the scar you would not know.
Day to day care post birth - she was a dream to care for despite being in heart failure and needed ng tube feeding and regular medication. Post surgery - she was fine.
We participated in early intervention and support - physio, ot and speech. Dd1 is and has made progress in all those areas. She is somewhat behind the 'average' child BUT she gets there. She was 3 when she walked - now she sprints
At almost 2 we moved to the other side of the world ( back to my home in Aus) Here she has a fab life.
When she was 2 1/2 and 4 1/2 we had two other children. How does her disability impact on their life - not that much - to both dd2 and dd3 - hospital visits, therapy visits are just what our family does - like other families go to church ( for want of an analogy) Dd2 thinks therapy is a place for her to play too. It is only now that she is getting a little older that we have had to keep her out of the room as she wants to 'help' dd1 and dd1 gets lazy then and lets dd2 do the work.
At 3 dd1 attended a mainstream kindergarten as well as a special needs kindy. Now at 5 she is in mainstream school 3 days a week and attends the sn unit 2 days a week. By the end of the year our goal is to attend mainstream full time.
dd2 wants nothing more than to be like dd1. SHe gets that there are things dd1 is not quite up to speed with but she deals with it. In fact she is quite annoyed that she won't have dd1's teachers at the sn unit and when I explained it was because dd1 has down syndrome and sometimes needs a little more help than she does - she came back two days later asking me if she sometimes needs a little help - I said yes - she says well then I need to have x and y as my teachers too.
Dd2 thinks nothing of coming to the office of our down syndrome association when I attend morning teas - she sees it as just playing with the other children - even though she is one of a couple of nt children - the rest have down syndrome.
As to other children - I have had one not so nice situation. At mainstream school at the moment - the kids all love her and argue over who is going to sit next to her at carpet time. They rush to tell me when it is her turn for the treasure box or if dd1 has done something amazing that day.
One of the reasons dh and I refused amnio etc ( other than my absolute dread of needles) was that we had first hand knowledge and experience of other families living with down syndrome. I know a young man who is my age - has a job, is a valuable member of the community in which he lives. Dh's former boss had a daughter with ds and their experiences taught us that Down syndrome was not something to be feared but to be embraced.
For us - it is part of who dd1 is - would I wish it away - no. Would I wish away the horrible judgey looks from others in public or the tsking when dd1 is trying to speak with people - sure, would I wish away the well meaning but trite - boy you have your hands full comments as if dd1 is an extra burden on our family - sure. I simply tell people we knew before she was born and that she was very much a wanted part of our family. Usually stops the judging or pitying comments.
This is probably a very long post but whilst it can be upsetting looking at the DSA UK website - I know dh found it great to chat with them just about dd1.
Even now day to day - dd1 is far easier to care for than dd2. As to dd1 and her two siblings. She adores then. SHe was a little too young when dd2 was born although she loves her BUT when dd3 was born last year it was all she talked about - her baby x. She was the first one dd1 looked for when she got up, came home from kindy, camme home from being out. She is also a little partner in crime with dd2.
I can tell you there are times I have wept - sure - what makes me the saddest - knowing that no matter how brilliant dd1 is - there are always people out there who think she does not have a place in our community or even on the planet. People who think dh and I were irresponsible for having her knowing that she would have special needs. People who think one extra chromosome makes her less of a person.