See lip-smackingly - WordReference Forums for samples.
Perhaps normally associated with food, appetite and the like (food is often referred to as "lip-smackingly good"), it's an expression of approval or satisfaction. Again, using the food example, one is said to "smack" one's lips after eating something delicious - it's hard to describe the action, but I'm sure we all do it without realising. Purse your lips together, maybe after licking them, and making a sort of kissing sound - that's lipsmacking.
So the newly-wed man is well satisfied, very pleased, as a hungry man would be after a hearty meal, or a thirsty man after an exquisite gin and tonic. He is, if you like, in matrimonial paradise.