Set up IceComm on a web site that only you and your kids can access, and give them the Chrome browser with a bookmark to go there at scheduled times
Very easy to set up server less video conferencing. Add a bit of TogetherJS to the mix and you've got realtime chat as well - without needing to install anything on any local computers besides the Chrome browser.
I use IceComm on my main server as the 'front door' to my business - I have a browser sitting on my front door all day, and whenever clients visit I'm ready for them. Its just like having a virtual front door to the business