Mall walking is fun!! I like to do that when I'm bored of my usual route or when the weather is bad. If I'm walking though, I'll make an effort not to go into stores until I'm done so that I can keep a pace. I love to people watch so I think it's a great way to get extra steps in the way!
Just a tip, since wannabeskinny mentioned it, maybe you could go in the morning to avoid big crowds, unless your mall isn't crowded at all, haha. Also, if you have a mall that has loads of stairs, that's a great way to get your heart rate up! I like to take the escalators and walk them up, I find them a little easier than normal stairs.
Also, if you tend to get hungry, make sure to bring snacks to avoid stopping at a café or a sweet shop.

Thanks for the tips Muguet