Distance is the key. To see a whole person with a 90mm lens will require you to be quite a ways back from that person. A 90mm like yours is great for portraits of individuals or pairs, particularly for head-and-shoulders pictures where you want to fill the frame with that person's face.
However, if you're going to be photographing a group of people and you want them to look normally proportioned, a 28mm, a 35mm, or a zoom lens covering those focal lengths, is the way to go. A basic zoom covering 28-105mm (full-frame equivalent, so 18-70 on APS-C) is the way to go for most wedding shooting. If you're shooting indoors a camera mounted flash will be a big help. Bring spare batteries.
Last edited by Oregon45; 12/23/16.
