Candy is one of the few things I'd be very reluctant to make with (particularly small) children. Hot melted sugar is not somewhere where small kids should be.

Though I'm not sure whether its traditionally swiss, how about a ganache based truffle type chocolate?

Here's a basic type of description of the process- http://baking.about.com/od/truffles/ss/making.htm

I've done this before with my small nephew. I did the part with the double boiler etc and had the ganache cooling before he came over. He helped roll the ganache, and dip it. He was about 3 and a half, and afterwards he gave it to mum and dad as a present.

Be prepared for a lot of it to be snuck into their own mouths though.