That's going to be a lot of lawns your kids will be mowing to cover the cost of repainting and cleanup.

Sell tickets.

I agree with RichardPencil. Make profits off of your children's worth by having people pay to view exhibitions.

That Sux! Classical Renaissance would be preferred at my house. But then, my crotch goblins just cost me security deposits in apartments for that. After those lawns get mowed, make them paint (with proper protection this time).

(1) Don’t leave permanent markers where kids can reach them… (2) Always save the paint remnants from when the house was last painted - That way you can touch up the paint… (3) Home Depot or Lowe’s or a paint store can match paint colors if you bring in a color sample. I had a friend who brought in a whole door once to buy matching paint! And they matched it.

Sadly, I expect this information is too late for you in this specific case but: If you have permanent markers in the building, kids or not, make sure you also have a whiteboard marker or two. On most hard surfaces (this is definitely true for whiteboards, ha not yet been false for me for painted walls, and may or may not be true for anything else, I haven't tried) if you can scribble over the permanent marker with a whiteboard marker before it's -completely- dry it'll generally wipe off just as easily as whiteboard marker alone would. I learned this the hard way back in an early programming job and was exceedingly lucky that one of my colleagues knew the trick and was happy to share so I could save the office whiteboard from my mistake.

As a parent who's had to clean up misses like that, permanent marker will run if you try to put fresh paint on top of it and bleed through the paint, you will need to clean up some of the permanent marker before painting, pure white vinegar and a magic eraser works really well.