Nice budget! But with that group airfare will take a big chunk if you cant find a deal!
My advice..with that group,
DDP, assuming most are over age 9, will cost a bundle for a length of stay over 5 days.
Last summer we stayed in a 2 bdr at OKW...6 of us, 1 a toddler...(we were nice and gave G Ma a studio)
ANyway....
we placed a grocery order with wegoshop.com...we stayed a week ...and this totally reduced our cost!
Now, mind you, thats if folks in your group dont mind making a few meals either! Some are totally against it....while on vacation.
I wouldnt do it every time...but with this group...that inc 2 teen aged boys...it was worth it!
However, we ued our DVC pts, paying Disney rates adds up..perhaps look into renting points from a member...that would be another way to get the most bang for your buck!
Good Luck!