Most annual plants have a long, hardworking bloom period. You need to locate the plants as soon as it is planting season in your area and get them in the ground (or containers) so that they can begin developing the nice root system that will support a few months of floral display.

What are the colors? Maybe we can make some 'tried and true' suggestions for you? Also, what kind of sunlight situations do you have?

She is using an almost burgandy/maroon color - I have seem petunias about that color that would work, but would like to find others, also.
The other color is a kind of salmony/orangy color (I would probably plant less of those), but don't even know where to start on that color. LOL
Thanks so much. rhizo. and anyone else who could help me.

Some African daisies (Dimophotheca) are close to a salmon-orange coloring. I've also seen a petunia variety specifically called salmon.

There are salmon impatiens. I've seen some dark red ones, don't know that they are really burgundy though.

Why not plant flowers that will contrast with the wedding colors, this may be easier than trying to match the bride and grooms colors..just an idea. Good Luck!
Marsha