take your bike into the shop and have them remove those things from your pedals, it's not safe. I suggest you buy an inexpensive pair of bike shoes first (well fitted hopefully) for you to get used to the idea. Later on, when you know what you want you can spend a bunch of money.
I bought a nice pair of bike shoes for about 40 dollars. they had a sole I could walk on and they were firm enough to protect my feet from the rigors of cycling.

ps in my humble opinion 25 pounds is a lot of groceries to carry on a bike. It would be enough for me!