I would definitely recommend going the managed account route. Talk to the NFA about requirements and filing as an exempt CTA. Just about any bigger FCM can handle doing give-up's to each managed account. It also will give investors comfort in retaining the account in their own name (and choosing their own clearing broker) and having transparency of balances and positions. The most common way to do this is to have your FCM set-up an execution account, have them APS (avg price) the trades, then send them a daily (or even several times a day) allocation sheet telling them how to split the contracts between accounts. I work with CTA's doing these things on a daily basis. PM me if you have q's.
How about setting up a model on Collective2.com that your friends/family then subscribes to (you can comp them)? They can then autotrade the model using whatever broker they want (that is supported). Each person has their own account, but you only enter the trades once. Also, each person determines how much they want to invest in the model. You can enter the trades into the model manually, or use their API... Just a thought. D.