I'm a female married to another female, and I proposed to her...
I bought two rings...one for her to wear, and one for me. We aren't fancy, so the rings were not solitaires (I was in graduate school, and that's all I could afford!), but they had little diamonds on them, and this way, we both had a ring on the appropriate finger...
In that same vein, I see nothing wrong with having a man wear an engagement ring, as long as it is a ring that he is comfortable wearing...why not? Show off the good news!!!