If you select for Air plus Hotel the box to enter they're promo codes disappears.
In a long winded email thread I finally got though to them what was broken (two weeks ago) but they have not seen fit to fix it.
They did confirm that the promo codes are valid, and have not been discontinued.
It looks like the only way that that you could use the 100 dollar promo code is to book though the 800 number. They were not clear if the 20 dollar "book by phone" fee would be waved.
Just an FYI