The unknown is scary.
I don't know if it's helpful but we still have family holidays: have flown to the States, Italy and France, eat out as a family once a week, have gone to a pantomime altogether, go to outside events and days out. We just carry on as normal!
He does need extra support but that means things like along with talking normally to him we use makaton signs while we talk / teach him a new word, concept or colour to make it easier for him to remember it. We also need to feed him when he's given up feeding himself to make sure he's had enough to eat (but then you do that with smalls anyway but with DS it's just been for longer that's all), he took longer to walk so we had to carry him and then hold his hand for longer etc etc
On a positive note - children with DS are a whizz at learning things visually and at 15 months he was able to correctly pick his name out when given a choice of 2 or 3 laminated name cards. He's 2.5 now and can read the letters a, b, h, m, b, j and s and make the sounds and correct makaton sign for each of them. That's more than I could do when I started school at aged 4.5!