My parents recently celebrated their 25th wedding anniversary, I was announcer and host for the knight, and it's the first time I've had family be more cheerful the more tipsy I was. Fluffing my lines got a cheer.

So I've got to ask, are you organising this wedding on your lonesome? Do you have any friends that might be assisting you?

My parents met through traditional (english and scottish folk) dancing, and so they had a dance instructor arrive. I'm sure there might be a western or traditional court dance instructor in your area, and the zoo will probably have an open area you can use to dance in. They will probably be able to do something fitting in to the steam punk style, my dad's 17th and 1thth century dance gear would fit right in.

It's also a great way to commence the dancing. Do you have a band organised? Does the zoo have any bands they recommend or allow you to bring one? Or at least use of a sound system or permission to bring one?

Instead of sword, maybe ask all your friends to bring a steampunk rifle? That might be a tall order, so instead, perhaps ask your friends to wear empty scabbards to your festivities, and provide them with long flowers or palm branches of some kind? A long lily flower stiffend by whatever a florist suggests might make a fine 'sword' for an honour guard and arch. And they won't sword fight with them, and if they do... it's a flower.

My Mum is jewish, so they have a ketubah, which my dad had reordered a much more ornate one that they resigned and now have framed on the wall. Maybe a nice big velum scroll for a wedding certificate might be possible? If not for the official one, then a nice showy one you can hang on the wall.

Also, At a Zoo, are you going to be able to drink? Will they lay on a bar?

Dancing and Drink are a must at any wedding where the entertainment of a fight (with swords or not) is going to be provided.

To quote Nanny Ogg:
Howto Have the Fight:—A fight is traditional at all Ramtops weddings, except those involving royalty, where the tradition is a small war.
Lots of people have asked me for advice about this. They say, 'Mrs Ogg, can you just rely on there bein' a fight?' And, yes, you gen'rally can. My advice is to make sure the drink is strong enough and that people are seated right to make it happen quite soon. That way you've got it over with and can get on with things without that naggin' feelin' that something's wrong. Once it starts, though, it's vital to see that it goes properly, viz:
Stage One:This is what some people call The Challenge. It starts as soon as people have a few drinks inside them and start to chatter, whereupon Man 1 will say, per'aps:
'What was that you said about our Lil?'
(This is only an example, of course. Other suitable challenges include: 'Hah, you wouldn't talk like that if you knew what our grandad told us about your mum,' and, if all else fails, 'That's my pint you're suppin'' (although this is considered pretty poor and suggests not much thought has gone into things).)
This will take us to Stage Two: The Question. Again, this is fairly
formal, but Man 2 can choose between a number of inquiries,seekin' to ascertain as it might be whetherMan 1 requires a face-ful of dandruff/knuckle sandwich/a nose that touches his ears on both sides.

The men will circle one another three or four times,which should not be difficult by now since both parties will be findin' it a lot easier to walk in circles. The crowd at this point are permitted a number of witticisms and shouts of encouragement, such as,'Kick him inna fork, our Sam!'
At this point one bystander,known as the Shover,will push one of the circling men towards the other (technic'ly this is Stage Three, which does not last long). This will result in some aimless flailin',but the first decently landed blow will result in Stage Four: the Wives. At a signal,the ladies associated with the men will each grab their partner and shout variants on 'You wait till I gets you 'ome, I can't let you out of my sight for five minutes!' Hitting the man over the head with handbags is ritual at this point or, if the reception has gone on for some time, a bottle may be substituted.

Stage Five begins when one of the ladies says to the other something on the lines of, 'I'm surprised you've got the nerve to show your face here, after what you did to Aunty Shipley!' and they then fall to fighting with rather more malign expertise than their menfolk, who bury their differences to separate the couple before something expensive gets broken.
The bride then cuts the cake