I know I'm ten years too late, but maybe this will help other moms like us starting out.
What we did:
Start with easy projects not complicated or long ones. Those aren't just hard on kids, they're taxing for the momma too. (or dad, if you're here). Small accomplishments help you achieve more success over time.
like having kids go on a hike and identify flowers, plants, bugs, etc.
you it first- easy stuff like common weeds and flowers.
then have them draw what they saw.
OR
Collect things to make a collage.
Keep repeating what you know and they'll get interested and take it seriously later.
it isn't art but small garden projects like potted plants (they can decorate the pots with markers even) and use easy growing plants like herbs (marjoram, mint, basil) helps them want to grow their own things.
Don't impose too many rules for the project. Makes it less fun and littles need that freedom to enjoy the art.
There's some pretty good general stuff on youtube. As long as you don't get too hard on yourself- eat the meat and spit out the bones. Do that with literally EVERYTHING on youtube. Getting started doesn't have to be complicated, give yourself grace and remember most of these people started somewhere.
( I edited this post because I got off on a gardening tangent - I have a lot of toddlers distracting me and I was initially on here for a gardening thing, lol)
Hope this helps someone.