How to get more students involved in business?

[DubstepLion1]

Our team has two divisions: Engineering and Business. Engineering has the Programming, Electrical, CAD, and Fabrication subdivisions with Business having the Public Relations, Marketing, and Media subdivisions. For a description of each of the subdivisions, please visit here.

Last year, in order to increase business participation on the team, we tried to do a system of primary and secondary choices for subdivisions. This didn't work as planned because of poor coordination between Engineering and Business. Members only stuck to their primary subdivisions and we couldn't force anyone to do something they didn't wish to.

With recently being elected Team Lead, I'd like to fix this issue in a way in which both Engineering and Business tasks get completed in a timely manner. Currently, we have 24 students on the team with 3-4 who would like primarily work in Business but hope to recruit more members in September.

What would be the ideal method of enabling a member to do Engineering and Business tasks simultaneously? What is the best way in getting more members to primarily do Business?