Curious. What kind of noise do you get when hit a large child? No never mind, I can't help with the seat problem.
But the soft top:
Mold and mildew are big problems for any fabric. You can fight it but it may always be there. But that said, the fabric in your top is pretty tough, so you can scrub it. I'd recommend elbow grease: a soft brush and mild soap (think dish soap, not detergent). 409 cleaner will help with mold. You may want to take the top off and scrub it with the fabric flat (they are hard to put back on when it's cold, though!).
With a 2005, that's probably a factory OEM top, and you can replace just the fabric and windows. Probably not what you want to hear right now, but always an option.