Effective PD with limitations

Hi everyone....I'd like to start a discussion about creating technology-related PD opportunities while also dealing with limitations. 

In my district, our high school and elementary schools operate on different schedules.  That makes it difficult, if not, impossible to get teachers from all grade levels together at one time.

We offer some after-school tech workshops a couple of times per month at both the secondary and elemantary levels.  I run into difficulty with a few things:

1. The district lacks standardization in technology.  We are working on making that better, but currently there are multiple brands of interactive boards, projectors, software versions, laptops, etc.

2. There is a wide variety of skill sets among teachers.  Some are more advanced and are bored when things have to be made simple for those that aren't as tech savvy.

3. Some teachers feel they need to be compensated in one way or another for giving up their time.  Currently teachers stay about a half hour after classes are dismissed for the day.  Our workshops usually last an hour or less.  This means that teachers give up about a half hour or less of their own time to attend.

4. I'm in a position to facilitate the workshops and have the freedom to schedule them.  However, I'm not in a position to require people to attend.

Given these scenarios and obsticles, I'm looking for suggestions to make our workshops as beneficial as possible to everyone that attends.  I'm also looking for ideas that will make people want to attend, even if they are not compensated.  After all, I don't think that giving a half hour of your time once or twice a month is all that much to ask for.  And finally, I'm looking for ideas to facilitate collaboration and learning among faculty members at all grade levels.  Providing training in a specific use of technology is one thing and it can lead to learning.  But I want to promote a broader view of learning technology integration.

I look forward to the discussion.

Matt