I dunno how close those are to 650 wheels, you'd have to get your hand on some to see if the brake pads still line up on them.

If by miracle 650 rims work, you can opt to relace, but that's an awful lot of work for a meh beach cruiser.

Otherwise it may be easier to soak those wheels in rust remover (can do one-third section of the wheel each night) and repaint.