First Welcome to Flyertalk!
Second congratulations to you and your wife.

It's doubtful that DL will budge too much on the refund or 6 month extension.

Reguardless of what you were told by the phone rep, most likely when you call to change your tickets when they reissue the tickets, if the fare is less you will end up with a voucher in your and your wife's name for the difference attached to your skymiles accounts.

Also what type of activities are you looking at doing? Tropical beaches are pretty much out, but there are lots of natural hot springs (even if your wife doesn't go in) spas in Western Colorado. Or Seattle is very nice, if you wanted to go on a cruise on the Sound.