Kefir is really easy to maintain as long as you can commit to taking care of it. You'll need to get kefir grains. Are you wanting basic kefir made with milk for you and water kefir for your kids or just water kefir? Water kefir is a different process involving a sweetener and dried fruit. I didn't keep mine up for very long because I was the only one in the family who like it. I've had my dairy kefir for a couple of years now. If you want help with dairy kefir I can help but I'll let someone else chime in on the water kefir.
This is an awesome website with tons of information. Don't let all the techniques and tips intimidate you though---it really is a very simple and forgiving process.