Another thing you should consider is Alsike Clover. It does well in poorly drained soils, the bees love it and I have read it doesn't need as much calcium to grow. I always see them on it, and if you mow it down it usually grows back and flowers again. I think we have white clover here as well, the bees seem to like it, but it doesn't grow around here nearly as much as Alsike, and it often doesn't seem quite as vigorous. However, that is just my experience, and we have a different climate and likely a different soil type than you.