I'd make the point that the school provides free parking for employees who choose to drive in. Those who choose to bike, walk or take transit in should also have their needs met (secure storage, and possibly a change room, locker to store walking shoes, umbrellas, etc...). A few parking spots or unused corner of the property could easily accomodate a lockable shed or chainlink enclosure, neither of which would be expensive.

If there's a secure storage area for faculty bikes, more might take up bike commuting. This could be especially persuasive if employee parking is a limited quantity. Other incentives to the employer could be recognition for participating in bike to work week, or some equivalent 'healthy workplace' program.

At my workplace, we have adequate bike parking, and a good shower/locker facility. About 15% of the employees bike in on nice days, and about 5% bike in no matter what, year-round. Since the average rate of bike commuting in my city (in summer?) is 2.5% of all trips, I think my employer can take a lot of the credit for the high rates of bike commuting we have. Our bike enclosure is usually full beyond the overflow point (there are also racks). If you're successful, make sure that the facilities you manage to get will accomodate a few extra users! You might be suprised by how many other people will bike, given the chance.