Hiya - I too have a little 3yo who was born with down syndrome and as TC/TB says also born with a complete AVSD - major holes in her heart - but operable. We knew about her heart defect before she was born and were told that in all likelihood dd1 would also have down syndrome.
We were still upset when she was born and the DS was confirmed - what upset me the most was knowing how ignorant and cruel other people can be.
Dd1 was fed by ng tube for the first 8 weeks of her life - from the moment she came home from hospital she slept through ( unlike her little sister!!) she was a dream to care for. At 8 weeks she underwent two open heart surgeries at the Royal Brompton and to look at her now - unless you see the scar you would never know.
As I type this she is watching Hi-5 her favourite TV show and dancing and laughing. Just like any other 3yo.
Downs Heart Group are FAB - they were so helpful when we were facing dd1's surgery.
YOu know - the biggest lesson I have learnt is that for all of the times you are despairing at something - they instantly disappear when your little one smiles, achieves a milestone.... our dd1 started walking earlier this year and you know - that was more precious to me than anything.
She now attends a sn kindy two mornings a week, goes to swimming once a week, and next year will be attending mainstream kindy for two days a week.
Here are some websites/groups that we found helpful -
parent group
my parent group here in Aus - links to info
here
If you want to cat me and then pass my details onto your sister - you are more than welcome.
The biggest piece of advice - love her, cherish her, enjoy her, celebrate this amazing life and the wonderful opportunities your family are about to experience.