It’s winter and we’re stir crazy

To parents of young toddlers, where are we letting them run around? It is absolutely frigid outside, 10 degrees, and can’t keep my 19 month old boys in the house all day every day. I want them to be able to run around, a wish that I would fulfill with my singletons by merely going to Target to get some shopping done. I could easily follow along after them and pick them up as needed, but with two, they’re inevitably running in opposite directions. Sometimes I will bring them to our local shopping mall which is invariably empty, because it’s easy to spot them, there’s not much for them to grab or mess with, and they can just run around a large open space. By now this has gotten old, so does anyone have other ideas that won’t break the bank?