Help!

You may scoff at my dilemma, but I need your help!  Let me first set the stage for you.  I have an overdeveloped respect for authority to the extent that it took a couple of years before I was able to address teachers at my kids' school by their first names.  My friend gave me great advice when I was struggling with this.  She said always to address a teacher as Mrs. Whatever in front of the children, but to go to a first name basis in private.  I remember the first time I ever addressed a teacher by name in an email.  I sat there at the computer and kept changing it to Mrs. and then back again.  (Can't imagine why I never get anything done around here when I am clearly using my time and energy so wisely.)  I finally made the plunge and I've been fine with it ever since. 

 Ok, we're almost to my dilemma, but first you need the second bit of information.  In striking contrast to the  blackness in my soul, I am a surprisingly perky emailer.  I'll be the first to admit that I probably make use of the exclamation point more than I should, but I like to set a light, friendly tone.  In fact, most of my emails to teachers start with "Hi Mary!" or whatever the teacher's name is. 

Now we arrive at my current problem.  David's teacher, who has a perfectly good first name, chooses instead to go by initials.  Let's call her P.J.  So, now when I email her, what do I do?

This looks weird to me:  Hi P.J.!
This looks wrong.:  Hi P.J!

Last time I went with this:  Hi PJ! which looked and felt better to me except for the residual guilt that came from having edited her name.

Aside from dialing down my perkiness (not an option!!) or only speaking to her in person, what should I do?