I wouldn't buy a couple a sexual gift unless they specifically asked for one.
It's not my job to "loosen people up" if they don't ask for help and I think if either of the couple were embarrassed or unimpressed with a sexual gift it could not only go to waste, but cause friction within their relationship.
A sensual gift that is very mild may be good, though. The JimmyJane Massage Candle Sampler
has 6 scents and is more fun than the boring old vanilla (that not everyone likes) that comes with the Knead Me Set.
Don't embarrass the man in this second couple. I remember years ago, when I was more demure about things like this when my husband and I received a few for our wedding, throwing away unwanted gifts with heavy sexual themes. The person's money went to waste. You can't change people until they are ready to change. (I've always like sex, but at that point in my life, I didn't want sex toys. People giving them to me didn't change me one bit, and the money they spent on the gift was wasted, because I got rid of these immediately.)
Stick with something more commonplace. You don't want to be known as "the chick who gave us the vibrating panties that went into the trash the next day" in this couple's injoke library.