Yes you can play with your children while wearing a dress. You can go down and be a slide, a climbing rack and cuddle bear. You can play 'turtle turtle" (which envolves wrapping a 4 year old in a heavy duvet and holding it while he escapes to the play house and giggles "I RAN AWAY". Or you can be a Lego playing mommy horse.
I often hear from women who say they wear sweatpants and oversized T shirts because it is more practical than a dress. In four years of motherhood to two rambunctious boys, there are very few things (like rock climbing) I have found that I can not do in an appropriate dress, and many a thing that I should not do in an oversized T shirt and faded yoga pants: like going to the store. I represent myself, my husband, my children when I go out of the house. And sure, I actually might not have had the time to brush my teeth that morning, but that does not mean I need to look like a non tooth-brusher. Oh, trust me, I do not look like those super fashionable moms who never have a hair out of place. Being able to actually use the hair dryer and style my hair luxury moment for me. And luxury does not happen every day. But it takes just as long, or even shorter, to quickly put on a pretty dress (or a pretty pair of pants and an attractive knit top), as it is to put on sweats. The name of these pieces of clothing speaks to their purpose: yoga pants are intended to do yoga. Sweats to exercise in. Unless you are doing either, they are not really suitable for the activity. Okay, yard work and deep cleaning the attic might be okay, but honestly, you can mop a floor as well in a halfway decent pair of pants or a nice skirt.
These clothes will get dirty of course, but so will your over sized T shirt. Both can be washed. And little hands with apple sauce are no less jarish to look at on a "Go Cardinals' sweater than on a nice blouse. So go ahead... no need to break out the pearls and heels, but consider what you give your husband to look at. You may not have a personal trainer and designer mineral water to sip, but you have a wardrobe (even if filled with trift store finds) that can show him you care!