Just tried it for you and both of mine can fit in there seperatly, not together. My boy is 4 pounds and my girl is 1 pound 11 ounces.
Both of mine just lay down in there, I'm not sure how comfortable they'd be for a long period of time if you kept the flap down since there aren't any air holes or anything like a carrier but for just running in and out of somewhere, if they'd lay down in it, I think you'd be fine. If you want pictures just let me know!
