If they're still quite small, put a radio mike on them (or one of the ones you get with recording built-in that you sync up later, I guess, is easier these days) and stand well back and let them play.

That's when you get the good stuff.

A couple of years ago when my son was a chatty, fast-moving toddler, his granny couldn't really follow what he was doing because she's a bit deaf and not as quick on her feet these days. Take him down to the park, mike him up, let him run around, stand well off with a long lens.

Also, because that's a Digital8 camera, it'll output analogue tapes over FireWire as described in the article. It's worth doing this even for Video8 because the output is so much cleaner than with capturing over composite.