Description:
Young children need supervision during garage sale activity. The extra traffic and distractions are a real hazard to them. At least one adult should be fully tuned in to the child(ren) at all times, especially the very ambulatory and curious young'uns.

Other comments or suggestions:
Older children enjoy participating in a sale, if they can make some money of their own. Determine in advance what is fair concerning their clothes and toys (separate sales tables, or kids drawing a percentage for their share of the sales items and their labor). My kids seem to be happy enough with a percentage, if I provide them with other means of making some Direct profit, such as selling lemonade and chocolate chip cookies. We usually sell the lemonade for 25 cents a cup, and the cookies at 2 for 25 cents. Mom usually loses a little money on this deal, because paper cups and chocolate chips, etc., are not free. I don't usually take a percentage on this, though; it's my means of keeping the kids nearby and out of trouble, and it's good practice in making change, customer service, etc. Other items that are appealing on hot days are snow cones, cold cans of soda, popsicles and popcorn.

This sort of thing is more successful when done in conjunction with a Neighborhood sale; it is way Too Funny to set up a stand with your kids, then take a walk 'round the neighborhood a couple of hours later and see how many lemonade stands have popped up like daisies! On a real scorcher of a day, we have given out free cups of ice water, just like Wall Drug.

Have the kids pick up cookies with small tongs, or with a napkin. Separating each layer of cookies with a sheet of waxed paper keeps 'em from sticking together and being squished, and also aids in minimizing hand contact.

Let the kids put up colorful signs advertising their enterprise. Ours is usually a piece of scrap lumber, with the writing done in sidewalk chalk. You could also have them use the sidewalk chalk to write "this way to lemonade and cookies!" on the street; supervise that, though.

Make sure the kids keep their jackets, shoes, and favorite toys Away from the garage sale area, particularly if the sale is a partnership of sorts. "That's not for sale" is not music to customer's ears; minimize having to say it by the way your arrange the space.
It's also a bummer if Dad or Aunt Susie sells your favorite toy by mistake.