Wipe off extra moisture and allow the cast to air dry. Try using adult socks of various colors to fit over the casts. You can cut them down or just roll them down to fit. They should be pink and warm. Any type of pants with wide legs is, of course, going to work better for you.
Sweats are wonderful.
If you're handy at the sewing maching, you can open up the side seams and perhaps add snaps. I have heard that Baby Gap has clothing which is on the loose side and thus suitable for a baby in casts. Nordstrom's will split pairs of shoes at no extra charge. Also try Parisians. Fill a small bulb syringe with warm water and syringe the water inside the cast to soak it off from the inside.