Is there a issur to kiss your wife, or show affection (not in an intimate way) in front of the kids?
Answer:
There is no prohibition of showing affection to one’s wife in front of kids.
Whether it is a good idea or not, and the extent to which it should be done, is a question that different mechanchim take different approaches to.
On the one hand, it is important for children to know that parents love one another; but on the other, showing intimate affection can lead to children thinking of matters that they should not be exposed to.
If the question is affection without intimacy, I think there is no problem, and where to draw the line is a matter of personal decision.
Best wishes.