Definitely agree with Jjeff1's suggestion about E-Rate. You may also be eligible for Title I funds depending on your school's situation. I know in the district where I work, some of the "poorest" schools are the most technologically advanced, all thanks to Title I funding. Have you considered getting some students involved? You might be surprised how many would be willing to help out with some of the labor for the less-turnkey solutions (let them handle editing, annotating, uploading, etc.). I know I would have jumped at the chance as a student, especially if I got credit for it.

While I have no personal experience with the program, I know people who participate in, and have had great success with, FLL (FIRST Lego League) is an outstanding program. I currently am lead programmer at the high school level for a team, and I know it's a great program at that level. As for platforms, I mentor an elementary team which uses NXT, with Robolab as the programming environment. I've never had any problem with it, and it's relatively easy for the kids to pick up on. The Robolab environment (based on LabVIEW fwiw) is very good for teaching logic and then relating it to robot actions.