How should I build my Frontend for a huge project?

Ive been working on building a non-profit, open-source organization for a while now and we have gotten to a solid point in the backend code. We have authentication, an event and rsvp system, profile picture generator, etc. If you want to check it out, you can here.

Im also working on a frontend, but Im at a stage where I can change the stack for it completely, so I wanted to hear your suggestions! You can check out the code so far here, and the domain for the website is fairfieldprogramming.org.

Do you think I should switch to react, pure html/css, or should I use vue? And how do you think I should communicate with the server?