As-salamu alaykum,
Acts of affection between parents (such as a kiss, holding hands, hugging) demonstrates affection, love and respect between parents. It also teaches children that marriage is one of kindness and closeness. Children feel more secure when they see their parents close and sharing loving moments. It also teaches them how one should be with their spouse. However, intimacy which goes beyond a casual kiss, hug or hand hold should be avoided. By this I mean, any kissing that is erotic or leads to sexual desire should be avoided in front of children, as children are quick to pick up on the parents emotions and these intimate sexual emotions should be for behind closed doors. I hope this helps!