I would also wait and see. I started chemo and still had hair 3 weeks later, it was thinner but not bald. I had it cut shorter but that's it.
After four weeks it actually became brittle and then broke off in places and my scalp was tender so I shaved it. You may still have hair on your wedding day.
I also bought a synthetic wig, a short cropped style which was very light. Everyone says it looked great but I found it hot, that could have been the chemo though as I had lots of hot flushes.
Congratulations on your wedding, hope your day is fantastic