For the stains, I would try a kitchen sponge with a little baking soda paste, unless it's too much area--if so, chances are a good shocking will take care of it.

You need to get some CYA in the pool--follow the directions per your SWG for how much, but I'm thinking it's in the 80 ppm range. Even if your SWG isn't generating yet, the Cl you have in the pool now won't stay without some stabilizer.

Regarding the bubbles, they're probably a normal part of kids splashing in the pool--we have them, too, especially when using the slide.

Janet