Bicarb and steam cleaning is your best bet if you cant keep the window open.
Unfortunately those of us who have pets are used to (or biased) to the smells so we dont notice them unless they are unually bad.
For example, I have 3 rabbits. Stitch is downstairs in a dog crate although out most of the day he sleeps on his blanket which is on newspaper (he no longer wees on this). He has two litter trays which are cleaned out every other day and I use newspaper lining, megazorb and hay.
The other two have a room of their own, the floor is laminate and they also have 2 litter trays, treated as above. I wipe their floor down each time I clean the trays out and leave their window open a crack most days.
Two or three days a week in this weather I open all the windows in the house for a few hours to air everything, and if we have guests coming before that.
When our guests come over they all notice the bunny smell
My friends are quite honest but understand that if you have pets you will get a smell.
Could you not take your dress to a family members? If not I would leave a few pots of bicarb around it to hopefully take away the smell and a week before your wedding get someone who doesnt have pets to sniff it. If it smells either take it to dry cleaners of air it somewhere :?
Good luck with the wedding though