[jimwick]

We are a regional team and draw kids from 6 to 8 different high schools plus some homeschoolers, so sustainability is always an issue.

In our experience it has been the adult mentors who have sustained the team over time. During the build season the kids take the lead, but in the off-season it's the adults who keep it going. We have a group of 4-6 adult mentors (some are parents, some not) who provide the "glue" to keep it all together. This group plans the open house, gets ready for the build season, does most of the fundraising, etc. So when the kids get there in January they are really just involved with the bot. In my experience the kids have too many other interests to be able to the necessary effort to sustain the team. Committed adults are more able to do so.

I hope this model can work in a school setting. If the school administration is able to give some real responsibility to "outside" adults it could work.
It sounds like your coach could use some adult help.