Side Effect is a good match for iPad mini
Took my iPad mini to the beach today in the side effect, it's a great match. The iPad mini fits exactly in the bag, and there's still ample room for all the other things you want. Bear in mind that there's no foam padding, so you can't carelessly throw the bag around, but as long as you use the waist strap you're probably safe.
As an added bonus, the side effect fits inside the main compartment pockets of the Co-Pilot so I leave it there for those cases where I don't want my full bag with me.