Trying to send Hawaiian Leis to Seattle was wonder if i can do that overnite pls

Yes you can

At an expensive cost. I would go in early or contact a florist to see how they ship their flowers

I don't see why not unless they have to be kept cooled than youn would probably need dry ice and a dry ice container Styrofoam or something lile that. Packaging has to be strong to protect it but next day air packages take a little less beating than ground packages.