Be aware that cruise prices vary enormously depending on time of year and the category of cabin you choose. Also the pricing is not very friendly for families of 5. Most cabins sleep at most 4. In order to all be in one cabin you have to take category 4 (or higher), which is pretty expensive. I suspect that choosing the Polynesian over another resort is the least of your problems as far as cost is concerned. At least there you can sleep 5 in one room!
Suggestions? The first that comes to mind is to pitch the cruise and spend the whole week at the Polynesian! But if you really want to do the cruise:
-- get quotes from other sources, including
Dreams Unlimited, one other *Disney Specialist* TA, and either Travelocity or Expedia.
-- do 4 day land, 3 day cruise rather than the other way around. That should save a few bucks.
-- don't let them sell you Unlimited Hopper passes, the most expensive option. Just buy 4-day park hoppers.
-- Book your own airfare, and decline
travel insurance and Disney transportation. With five people you can probably do better with private transportation or car rental.
-- Can you be flexible on the week you go? Ask about finding lower rates for cruising on a different week.
BTW it cost us (booking ourselves) about $5000 for EVERYTHING (incl meals, tips, etc) last year. We could have done it for less, but we only have 2 adults, 2 children. I doubt you could do it for less than $5000, but you should be able to do better than $7000.