If you are worried about ethical or legal concerns in running a presale in your current situation, just be very upfront with people the same way you are with us. Price yourself at a point where the people who take early risks can see 100x (or higher) returns "easily" given your understanding of the market and your business. People are willing to put money into a 2 man team with a dream, but you might have to lower your expectations of how much they are willing to put in.
Concerning the legal aspect, we have found ourselves in a difficult scenario in which we need to register the corporation, which we did not want to do because it is built on the DAO and is fully decentralized. However, after much deliberation with legal organizations, we decided to register the company as an LLC company with a forming a trust for the management entity with the stakeholders being the beneficiary.