first of all - you will need 2 hotel rooms if you go the hotel route - go look at
www.skyauction.com
you will need a 2-bedroom that sleeps 8 (not 6) - so kept that in mind when you decide to bid. remember that you need to add their charges for a timeshare it will be $195 + $15. Only bid on the 7 days ones.
most of the hotels in the Kissimmee area will run around $30 to $80 a night - but you need 2 rooms for 8 people.
Transportation is another thing - they may furnish buses to the parks - but the buses generally stop at other places before they go to the theme park - and they generally only go once or twice in the morning and the same in the afternoon. if you want to see the night shows at WDW - forget it.
get a car - yes the driver would have to make multiply trips - but it would be worth it - of course you could get a van for everyone but they generally cost alot more.
Only the top of the top offer airport transportation - even WDW does not - you are charged and it is Mears. Come to think of it I don't know a hotel in Orlando (besides the one near the airport) that offer free airport transportation. the airport is pretty far from the theme parks. So renting a car can help here - again multiply trips....or rent a van....
good luck!
also go in the off season - lower cost of renting. Sept or Jan - you might find the All star (a WDW resort) for $59 a night - so for around $132 a night you would get great WDW transportation - of course that is if WDW offer the same discounts this year that they did last year.....but you would still have to pay for airport transportation.