For 12 of you I would say you definitely need a house...can't imagine one condo or townhouse would fit everyone.
You should be able to find one that works for you. Do you prefer to be closer to the parks? If so, try for one in Windsor Hills, Emerald Island or Windsor Palms for starters. All are very convenient and very nice.
You can go a little further out towards Rt. 27 and you can save some money too but it will take you longer for your commute (approx. 15 min or so but traffic can vary) It really depends on what is important to you.
To get an idea of availability and pricing you can try
www.windsorhillsrent.com and plug in your dates. Be prepared for an overwhelming amount of responses however.
Is your party a mix of adults and children? Be sure to read the bedroom layouts of the homes you are interested in to make sure that they work for you. Most 4 bedroom homes for example tend to have two master suites with one king or queen size bed and en-suite bathrooms and two other bedrooms that typically have two twin beds in each or possibly an extra bed using bunks.
We have rented twice before using
www.vrbo.com going directly through the owner. We are also going this summer and used the windsor hills rent site and also booked through an owner. It's always worked out well for us.
Good luck and post back with any questions.