Wedding Wire Website Control Users

I have a wedding wire website set up and was hoping my fiance could join in on the fun if he needs too (such as filling out his profile, making adjustments, anything really).
Then I was hoping to give access to my maid of honor. She's doing my Jack and Jill so I think it would be appropriate if she was able to put updates on the site.
How do I invite other people to become admins? I thought I found it once before, but my fiance said he never got an e-mail (unless I used an old one of his). I also saw there was no option for giving the maid of honor admin access. -Is it okay if she was the "mother of the bride" or something?
And lastly, do these people need to create accounts with wedding wire? If so, will they have easy access to the site? (I kinda hate making them sign up for a bunch of different things, adding more passwords for accounts for them to remember) @__@