I don't know if the following would be practical for you in your facility, but when I was the clinical educator, I had a cardinal rule NEVER to do inservices at change of shift. It might get the most people, but the retention (or appreciation) is rarely there!
I also instituted a staff education white board/cork board, posted it in the nurses station, and tried to keep it fun. I would post a question every other day (eg: "What antibiotic, if rapidly infused, is associated with Red Man syndrome?"). Sometimes I would do the word of the day (eg: "intraosseous") or post what I called "From The Good to Know Files:" and post a blurb about a policy or a new piece of equipment. A pack of gum or a candy bar was the incentive - so small, but it worked! Keeping the board fresh and updated was fun for me, and interesting but non-threatening for the staff. In fact, some of the staff started submitting their own questions/words of the week.
I wish you luck with your endeavors!