If the project has momentum then the absolute worst thing that you can do is resist adding additional people to the project. If you do not understand how additional people can increase project velocity and add value then you are not experienced enough to make that decision and it will show to all of management. What you need to do is be strategic about how the team grows.
First you need to think deeply about what you do not know. What are the organizational hurdles you are likely to face? At what stages of the project will you be over-allocated as a resource? How many presentations and one-on-one conversation will be necessary keep momentum? How will this project be monetized? How will the end product integrated into an existing offering? Or how will the end product be marketed and sold?
Once you have a good inventory of what you will need, sit down with management and talk about how to address these needs--this alone will earn you a lot of respect. Ask who will likely be assigned to the project. Start taking these people out to lunch to discuss the project. If they are more senior they will generally offer to pay. Don't hesitate to pay even if out of your own pocket. It will show how committed you are to the project and organization. During these lunches ask questions about the process other successful projects have gone through and the types of problems your project is likely to face. NOTE, it is critical to not be defensive or offer too many pre-baked solutions during these meetings--it will come of arrogant, dismissive and impulsive. It is much better to say things such as, "I have some thoughts around this, but need to vet the ideas with people who can really help shape them." You will have opportunities to solve the problem in due time, or even better to have other people "solve the problems" with your solutions.
Ask if you can be a part of the decision making process for attaching additional people to the project. If you are included, be very judicious using any perceived veto power. It is better to raise concerns and shape involvement than to try to establish a front. Of course, there are always cases where lines should be drawn, but if you have voiced realistic concerns then you can keep management up to date if you seen things going awry. If you are not included, accept that decision maturely and remain engage in the process. You will likely have more influence on the side lines than you realize.
As the project grows you will need to find an exit from your technical role. You will need to own the vision, but you will not have time to execute all the technical details. Mentor people to take over the details and build as many documented repeatable processes as possible.
Learn how to present your ideas. You will likely be invited to more presentations. Know your place in these presentations. You have more to lose than gain if you say too much. Be there as the "guru with upside" instead of being the "one-hit wonder" or the "wild card."
Good luck! I hope you do well. Don't be afraid of not knowing something. Nobody knows everything. Embrace other people's capabilities especially when you don't understand what they do or who they can help. These are generally the people you really need.