EDIT: make sure with management you can decorate the night before, most places have rules and other parties happening

I did my flowers for my engagement party and my shower. I used orchids, calla lillies (engagement) and red roses (shower). I didn't do my wedding because of wedding nerves and stress. With wedding nervousness and last minute preperations...flowers were not my focus. But it's possible and may save you a ton of money.

I'm not a florist, but from my experience these flowers last forever. The key is to get REALLY fresh flowers, I'm not sure where your getting your flowers but I told my florist to make sure their fresh. Can the wholesale people help with that? Or try a supermarket, that's where i bought the roses and the girl helped me with coordinating.

I did the arrangement the day before both parties, and both were refrigerated the night before. I do think they'll be okay because my flowers lasted weeks after the event!!!! We gave them to guests and the said they were really strong and healthy. Out of the 2 arrangements (mini calla lillies and cymbidium orchids lasted longer) 3 weeks after the wedding
Roses (one week) Can you do a test on 1 arrangement?

I'm trying to remember what helped me

I didn't fill the vases very high with water overnight for transporting, they need enough so the stems are touching the water. Fill them up when you get there...

The first arrangement took longer because I wasn't sure what to do??? So be prepared for some flowers to be more managed and may break. Ugggh. Once the first is done the rest are easier.

I looked at lots of pics of arrangements online for inspiration, when i did the roses i referred to
http://www.jamaligarden.com/index.asp
Jamali has beautiful vases in natural fibers, ceramic, glass
I used low long reactangular vases. This place is known for florists in the industry in nyc.

I also knew ahead of time what I wanted
http://ovandony.com

Ovando has great architectural arrangements with long Bear Grass leaves (which is cheaper than flowers and you can buy online) and minimal flowers, they charge soooo much for so little. But they don't look too hard, look under shop online and weddings for inspiration.

I love the arrangement called perfect balance
look under ovando-shop online link
1st row, 4th column

They have grass, orchids, cut succulent very minimal but beautiful. I wish I did these for my party...

Good Luck