Apr 18, 2014 - 8:15 AM
You'd better check the webcams on the local TV channel and the weather forecast right before you go up. It can be beautiful up there if it's a mix of clear moments and some snow, but with only snow fall you won't see anything. There are several places at the Jungfraujoch to enjoy the view while staying indoors (the restaurants and the observatory for example), so you can choose to do so if it's too cold. If it's not too windy it shouldn't be a problem to go out for a short while though.
Note that young children with medical issues (e.g. ear issues or breathing problems) should not be taken to altitudes like the Jungfraujoch. Healthy children should be fine for a short stay. More information is here.
Have a great day!