I remember one where Mary Jo and Julia take some little girls camping and want to show them the joy of living without modern conveniences. Suzanne is also there, and starts putting makeup on and all the little girls are fascinated by that much more, and Mary Jo feels hurt.
It's been some time since I've seen it, so some of the details may be off, but I think you have a good idea.
"Bullsh*t rules!"
-Cher in Mask
Off the top of my head I think you may be referring to the Season 6 episode I Enjoy Being A Girl. It has Carlene, Julia, Mary Jo, and Allison escorting a a group of Girl Scouts, of whom Carlene is the leader, on a wilderness trip. It's a very funny episode. One of the better ones from the final seasons.
I'm going to assume that is the ep you are looking for. The only other DW episode that bears any resemblance is The Wilderness Experience. But there's no children in that one, so, I dunno...
The I Enjoy Being a Girl episode was on TV Guide channel a couple of weeks ago. As Aztec Camera said, I think this is the episode you are referring to.
Mary Jo gets upset and feels hurt when the young 10-year-old girls go off with Allison to give each other pedicures. She's upset that the young girls identify more with Allison's interests in grooming and beauty products than with her interest in sleeping outside by a campfire.