I purchased both kits from ACA and cannot find the paperwork to relay the cost. I also purchased a plastic cover for the hole in the floor.
The PTT switch is located at the top of the stick. It's basically a two wire spade terminal switch. To remove I unscrew the nut (securing the switch) on top of the stick and the whole thing slides down the inside of the tube as you pull the stick out. The trick is to get the switch back up to the top of the stick when you re-install. I roll the foam rubber grip back and slide the black rubber top off of the stick. Then you fish the wire and switch up through the stick, re-install the nut, slide the black rubber top onto the stick and roll up the foam rubber grip.
Your POH should give the weight of seats and cushions or ACA can tell you. I'd say it's between 20 and 30 pounds.
I've had a bicycle and a weeks worth of camping/riding gear stuffed in the back of my plane--all secured with webbing and straps.
One last thing, you mention "stuff and the kids" in your post. I think the FAA, and others, would take a dim view of you hauling "the kids" unsecured in the back of your plane. I think you can purchase an extra wide seat if you are interested in hauling 2 small passengers.