Maybe you can have the kids decorate a border of rocks,brick,etc.with paint,and have them help place the items to help remind them. I find that if I make it their "special" place too, the kids tend to be more careful.
As for the dogs-if you figure something out let me know--no matter what I do-my dobie still goes and tramples and digs my seedlings and bulbs
Good Luck

Try spritzing the dog with a water gun you keep hidden in your pocket when he goes into the beds. Dogs hate getting spritzed, and if you add to it hollering and shaming they learn extremely fast.

I think i'm getting the point across to my four year old now. I have been involving him more in the garden so he has a vested interest in it. My two year old just wants to copy everything I do so if I start to dig he's gotta dig also. I think I might be able to teach him to dig in his special area( an area with unimportant plants in it).

Explaining to my 3-year old daughter that she can help the baby plants grow big by talking/singing to them (and not stepping on them) seems to work. Unless you dont want your kids talking to the plants....I think its super. :)

Step one: Go to home depot. (preferably without your kids so you can have a break)

Step two: purchase roll of plastic fencing for less than $20 and a pack of wooden stakes

Step three: pull out the handy dandy staple gun

Grand Finale: stick stakes in ground around the garden, have someone help you hold the fencing while you staple, and viola! dog free and kid free.

PS- hollering and shamingmay work for the dog but is useless with a 15 month old. been there done that ;)