Oracle is correct re: Mr. Clean's 'Eraser'. Follow the directions on the box; Eraser must be damp or squeezed well. The quicker you want to get the cleaning job down, the harder you press, but I've found that this also tends to take the finish off of things. It literally erases marks. Case in point: footprints which won't mop off on linoleum. It gets into all the little pores of the linoleum and gets the dirt.
With the vinyl couch, there shouldn't be much of a problem using this method to remove the marks; vinyl seems pretty strong. If the stool is also the same vinyl, it should be ok. If the stool is wood, you could leave the drawings on and call it the "family stool" where the children draw, but I am guessing it is vinyl. It depends on how you view the incident. If you value the kids' creativity, you might show it off. If you feel affronted by them doing it in an inappropriate place, though, then I would show them something they are allowed to draw on and use the Eraser.
Hi there... I used to hang out with a bunch of guys in a car club. The guy's place where everyone seemed to congregate told me he actually used Dawn dish liquid to get grease out of the clothing, etc. I do have a container of that special goop for removing automotive grease, but I like Dawn better... plus Dawn has these cool scents out nowadays. My husband's hooked on the Apple scent.
I would first read the owner's manual to find out whether the leather used on the seats is washable--it should be or a lot of other guys will be in the same boat as you. What kind of leather is it? Soft like sueded leather like they've been using on jackets ("bomber" jackets) or harder, shiny leather?
As when washing anything new, I would do a spot test in an inconspicuous area. If it looks or feels fine to you, then proceed. I would not place it in the washer machine unless the leather covering the seat comes off and has a tag with machine washing instructions. Even then, I would still pre-treat the stain by dabbing at it with a solution of Dawn and water.
THAT is the thrifty way to do it. The more expensive way is to buy those special cleaners at like Advance Auto Parts or Autozone and follow their instructions--make sure that they are ok for leather. Any method you use may result in a loss of color, of course.
Last course of action would be to either find some washable leather covers for your car that slip on over the old or choose a different seat cover.
Seriously, though, I cleaned my husband's SUV that has leather seats that were smooth and Armour All has these wipes you can use. I don't know whether there was grease on them other than dirty hands, but they looked nicer. Yes, I would have trusted a couple of drops of Dawn in a bucket of water to these leather seats, but they were hard, smooth leather.
