Do me (and yourself) a favor. Please, PLEASE, skip the appointment you had to get a spray-on tan. Go ahead if you must and get the regular tanning-bed tan, but I implore you, don't get the spray-on variety.
Why?
Because you will be orange in all of your wedding pictures. Not just a little orange, but Oompa Loompa orange. I am not kidding on this one.
To the eye, the spray-on tan looks just as good as a regular tan, but to the camera you will just look orange. Everyone else who didn't get a spray tan will look fine, but you will be forever orange in all of your wedding pics.

See the picture above. This is EXACTLY what you will look like. I'm not exaggerating. I would post examples (I have many) of real brides with spray-on tans but I don't want to embarrass any of my clients.
BTW—If you are a recent client of mine who did the spray-tan thing, I'm not writing this message about you. I'm not writing this message about anyone in particular, I'm just trying to avoid a lot of future heartache for my clients. The fact is, I can fix the orange tint, but it has to be done by hand and won't be covered in the standard editing and color-correction that is included in all of my packages. This type of retouching is done at an hourly-rate.
"How much is it?," you ask.
Don't get a spray-on tan and you won't need to find out.