can stockholders in a professional corporation be in a cafeteria plan? or would they be prohibited as self-employed? If they owned 10 percent or more, would they be prohibited?

Are they an S-corporation or a C-corportation? If an S-Corp, and they each own 10%, they could not particapate ( the rules being they may not own more than 2%). If it is a C-Corp, they could participate, but you should be watchful of discrimination issues.