Not a strange request at all. BTW, best of luck planning this trip...it takes a lot of patience and understanding to co-ordinate a group!
Check vrbo.com, if you haven't already done so. It is fairly easy to search. Look for the area "Kissimmee Central West" enter your size requirements (6+ bedrooms) Emerald Island Resort is showing a couple of 7 bedroom places available for those dates, and one is fairly reasonable, in my mind.
Now, given that you are travelling at a PEAK time, you know you will be paying High or Holiday season rates. Ouch! And that parks will be crowded. Very crowded. Weather will be hotter than heck. You certainly will not need to pay for pool heat.
Emerald Island Resort is a decent location. It is about 10 min to WDW, and about 25-30 to Universal and Sea World areas. You will find convenient stores close at hand. Kissimmee is definitely our preferred base when we travel to the area. There are 2 Formosa resorts which a bit closer to WDW, as well as some others, but not all offer 7 bedroom homes.
A word of warning, many owners will adhere strictly to the posted max # of guests, due to fire regulations, so try to steer clear of any which sleep up to 14 if you have 15 guests, even infants.
This may sound a bit negative in tone...it is not meant to be so in any way! Orlando is my favourite vacation destination ever, and you will have lots of fun. Having stayed in vacation homes a number of times, I would never go back to a hotel room. In fact, my DD & I ended up in a 3 BR condo for just 2 of us...it was competitively priced and we really enjoy our own space. LOL. But do be prepared for the heat and crowds.
