As with the formation and running of other kinds of businesses, you have a number of considerations gong on here: the need for limited liability protection (which your current general partnership status does not provide), tax issues (the treatment of which vary depending on the entity you choose), financial issues (the costs of perhaps forming separate companies for each subsidiary), and other interdisciplinary legal issues that may touch on U.S. and international taxation, banking regulations, the Investment Company Act and other securities laws.
In addition, you will have management issues that must be dealt with in some form of entity ownership agreement (among other investor-related documents). For example, what if Subsidiary #1 doesnt perform as well as Subsidiary #2? Are all of the members willing to take the loss? Are you adequately disclosing these risks to new potential investors?
Make sure to get advice thats tailored to your situation--this is definitely an area where you do NOT want to rely on what you find on the internet alone.
Nina L. Kaufman, Esq. is an award-winning New York City attorney, edutainer and author. Under her Ask The Business Lawyer brand, she reaches thousands of entrepreneurs and small business owners with her legal services, professional speaking, information products, and LexAppeal weekly ezine. She also writes the Making It Legal blog.