Try as many of these as you want to, figure out which ones work best for you and your family.

I’ve grouped them for the three benefits, but you’re welcome to mix and match however works for you

Here's a selection of downloads and printables to make learning mindfulness more fun for you and your children.

Each child is different, but I would suggest anywhere from 3 upwards. Older children will be able to focus for longer, but there is benefit in starting young, while a child's brain is developing.
The sweet spot is probably from 5-10, but older or younger are definitely able to partake and benefit.

None at all

No

You could probably complete it over a day or two (in short bursts), but spreading it over time could help it to soak in. You can keep returning to the course as often as you like.

No, the course is easy and fun.

No, only yourselves and an eagerness to learn.