for my beach cruiser breaking spokes was pretty common. I would replace them as they broke along with re tightening all the ones that needed a good turn or two on a truing stand. They were still breaking... I completely de-laced my wheel and rebuilt it replacing 7 broken spokes.
So far soo good but I donno how much longer it will last. I had zip ties on my spokes where they X each other that seemed to help for a bit. Going 14 gauge spokes with a stronger rim may be an option the weinman wheels I found on amazon seem to be built like a rock and are surprisingly cheap double wall, 14g spokes, (generic) shimano coaster hub. You can get the set from amazon (before tax shipping) for under 70$ here is a link if anyone is interested. I saw a set of these first hand in a local bike shop and just love them... they however wanted nearly 160$ for the set haha... go amazon!