I can't offer any suggestions...but just to say that it must get better as they get older! My ds's are 14/11 and myself and I do only 2 loads a WEEK for clothes and then one for bedding/one for family cloth/towels (I wash the FC a hot wash then add towels. We use cloth for everything and we homeschool and live in the boonies with animals so we're getting dirty. I'm sure when new babe arrives I will have more just with cloth diapers and probably another load a week. And I shouldn't even say "I" do it, as the boys do all the laundry!
But I think what really helps is that my ds's and myself have a very limited wardrobes. We usually wear the same things multiple days though we shower/bathe most every day (except for 11 yo which is every other). So we have underwear/t-shirt new every day, but we'll each use our same towel for showers for the week and hang them to dry in between. But we each have basically 2 pairs of jeans (1 good/1 work), few t-shirts, few long sleeve shirts, socks/undies, and then 'leggings' type pants we wear inside. I usually wear a skirt over those or the boys have sweats and/or wear shorts over them in winter as they love their shorts. Then of course we have some special occasion stuff and summer wear. But, our regularly used in-season clothing fits into ONE dresser (six drawers) and a small single door closet for the three of us. We used to live in a 200ish SF motorhome so they are used to limited clothing choices/space. And they maybe because they are boys, they care as much about what they've got on as long as it's appropriate to the activity? But also homeschooling means they aren't big trend followers either. My oldest is dx Asperger's/Tourettes and is sensitive about clothing, but he got to pick what he has and it's just what he likes. I find that having less choices makes it all easier too. You just have to put on what's there! That's all there is!
They are also old enough to understand there are 'dirty' clothes for outside play and then 'clean' clothes for inside and to switch in between.
This time of year, they usually wear sweats or 'leggings type pants', t-shirt, and a sweatshirt inside. The sweatshirt they will likely wear all week as it's just over clean clothes. And if they spill something on it, they clean it up with some water/handsoap and keep it on or hang to dry if too dirty. They have a pair of jeans hanging in our mudroom that they put on to go outside and play/work. They usually just pull on over the leggings type pants (they'd die if they heard me call them leggings...they are boys! LOL) and then when they come in remove and hang. The jeans only get washed 1x a week. So, your suggestions of an apron/pinny for your girls would probably help keep them cleaner!
If we go to town, they will pull out clean jeans/shirts/etc. but when we come home, at least the jeans get hung on a hook in their closet to wear again when needed. Shirt may or may not depending how dirty they got in town.
Also how I've cut down on bedding laundry is that each bed has a sheet/pilllowcase/duvet cover and I can fit all three beds (all fulls) into one load. The duvet covers I made by sewing together two full size sheets and then a fitted on the bed. I got all the same solid colors for fitteds/cases and did the duvets different for each of us. But no blankets/quilts/top sheets/etc. to wash also. I wash the down comforters a few times a year.
So, I don't know if that helps....but it will get better as they get older I think!