First, let me say as someone with experience with this... you should make sure that they will let you bring your own alcohol to the winery. You probably already did that, but it is something that I felt I had to say. Disclaimer: I've not done this, the place that we are getting married will not allow us to bring our own beer.
Now, to answer your question.
Kegs: If you are OK with used kegs you can save a decent amount of money there. Check out
http://www.cornykeg.com/ ... you're looking at about $150 in just kegs.
CO2: You'll need some type of CO2 source. I would go for a CO2 tank if you have the money for it. The tank will cost $80 when you are all said and done probably. But, I know there are places that will rent them to you.
Regulators: This is where you need to decide how many times you are going to use this set up. Do you want all of your beers to be set to different carbonation levels? Are all three beers going to end up being about the same? The difference is needing a separate regulator for each one (~$45 each). If you decide to just buy one regulator then you need to buy a air distributor (~$30). Section total: between $75-145.
Tubing and fittings: $.50 per foot ish. What do you need... 5 ft from CO2 tank to keg, 5 ft from keg to jockey box.. times three.. $15?
Way to keep it cold: You could build a jockey box. If you are handy, build one. Buy a cooler ($40), 3 faucets ($100), a cold plate ($100) (I guess you can get them much cheaper on ebay, but I'll put a link to one you could get from a store here so you know what I'm talking about), and miscellaneous fittings.
Faucets:
http://www.beveragefactory.com/draftbeer/faucets/faucets/EBCFBLSHANK4.shtml?CAWELAID=1372128042&CAGPSPN=pla&catargetid=320012430000187825&cadevice=c&gclid=CjwKEAiAxsymBRCegqiLzI7Q1S8SJADOgQrzgMSNYqz-iFXdJsFLFtwlKE0tOw_He5qX_SSgRhMs_RoC3-zw_wcB
Cold Plate:
http://www.micromatic.com/draft-keg-beer/jockey-boxes-pid-CP-0814-3.html
If you can't make one, you can always buy one.. but wow are they expensive.
http://www.micromatic.com/part-pid-HDCP-D2-48B.html
Places to save money:If you are just doing this as a one time thing and want to save money, you may want to think about "keg conditioning" and using the handheld CO2 things instead of a tank... like this:
http://www.cornykeg.com/product/hand-held-co2-ball-lock-keg-charger-kit/ . That will take a bit of work, but as long as you keg condition you shouldn't have any problem with getting flat beer. Saves a CO2 tank ($80), regulators ($75-145). But, if they aren't used right they can be dangerous.
I think total, you are looking at like $650 or something like that.