1.Make a fuss of them.
2. Tell their Mum how gorgeous they are (because they will be)
3. TALK TO THEM
4. Be daft with them
5. Look at them.
6. Ask them what they are doing at school, or any other question you can think of come to that (they might not answer, but their parents will and they will feel like you care)
7. Tickle them, stroke their hands, pat their head.
8. Ask if you can have a hold/cuddle.
9. Smile and laugh with them. Try to make them laugh.
10. Take photos of them enjoying themselves, cos it's cute.
10. Find out what they like/find a favourite toy and PLAY WITH THEM!
11. Don't focus sole attention on siblings of said child or any other children that may be around. They are there too, and just as important! Disability is not akin to wearing a Harry Potter style invisibility cloak, so don't act as though it is.
12. Above all have a bit of empathy and think what you would want if that was your child.
Oh look! How funny/incredible!! The above list could equally apply to any child, disabled or not- who would have thought it? It's almost like I'm suggesting you treat disabled children as you would any child. Fancy that. Disabled children, though perhaps limited in their ability to interact are not newborns that you don't really need to bother with, just because the appear to have limited capacity to understand or respond. They are actually understanding more than you can dream of as you carefully and desperately avoid their gaze. Try opening the lines of communication, you might surprise yourself. You might realise how amazing these kids can be, if you just give them the chance.
I know people from the ages of 8 to 83 who can mange this.
Maybe you can too