My suggestion, in a meeting only 2 people should go. One from business side and one from technical side but who understands business as well. For the first meeting, you certainly aren't going to close all the requirements then n there. First get to understand the requirements from the client side and ask technically apt questions to understand what all will come under the scope of work.
The scope of work from Business side can be as simple as registering a user into the system, but it might add more work in case the client says that you need to take care of CSRF. Now this would mean that you will have to implement a token for every request and in case you open the same page in 2 panels then one will have to logout etc etc. So having a techie might help.
Since you have already secured a meeting and I believe this is an advance level meeting and lots of discussions have already happened over phone or email, I believe you know how to sell stuff. If the previous statement is true, ignore reading rest - 2 people meeting is decent, taking all 4 for the first meeting might seem too desperate. Do not show this up to the client else you will lose all negotiation power. No matter how badly you want that project, just do not show it up.
All the best for your meeting. Do let us know what happened and how many people did you take and how it help.