Weddingbee boards

I need advice! I work at a small library (about 25 people) and am getting married over a holiday. I am also getting married a 6 hours drive away. I have no problems inviting everyone since i know only a very small percentage of them will attend but I am not sure how to invite them. I asked a coworker who had a casual wedding, and she said she just posted the invite on the communial board. My wedding is semi-formal and this seems like a big no-no after reading through posts.

The issue is that some coworkers I feel a lot more comfortable inviting than others and would have no problems sending them an invite to their homes, but for others I feel like it would be odd to personally invite them (for example, there are some shelvers that I have only met twice because we work opposite hours, but I wouldn't want them to feel like they were the only ones left out).

Would it really be horrible for me to post the invite on the board instead of mailing them out since other coworkers have done it (plus there are only two coworkers so far that have mentioned that they may make the drive to the wedding...)