I went through the same thing (also with Sunwing)... our quote was only good for a few days and then we would've had to re-quote.
I decided to go ahead with it and for ease/speed, I put up an e-vite page to spread the word and collect responses. It was pretty stressful and I felt that it was a bit of a pressure tactic by Sunwing, but it was a one time sale and I checked with a few other TA's who all confirmed it was a good rate/sale.
In the end, we got 26 people who booked (and have to pay the full amount by October) and probably another 20 people who are going to wait until next year and try to book.
The rates you posted above sound about right to me for that resort, it was one of the ones we looked into as well.
And Sunwing doesn't have great children's rates, so we're waiting to see if those go down before any of the parents with children book. There should be some promotions - because seriously, how much do kids eat/drink?!