If you have any doubts about your teams ability to create the game why not start by making something on a smaller scale to gain experience and funding towards your big dream project?
I’m not as hugely experienced as most in these forums but I have a good idea of the scope of a project like this and its a massive commitment for each discipline in its creation. It’s unlikely you’ll have the same team working on this project 2 years from now, people will leave due to new commitments such as family, work, travelling, etc. and keeping interest in the game may be difficult when/if key members drop out. This is more a fact of life than anything else.
If you start a smaller project there’s a better chance you’ll finish it and you can focus on creating a complete and well realized product that will be a much better credit to everyone involved. Doing this will give you time to decide if you can work well together as a team and begin a new project with much more experience and funding or maybe you’ll want to go your separate ways with a fully complete and released game under your belt.
Good luck whichever way you go with this.