He first denies it because he really does see something wrong with it.
Truthfully, there is nothing unusual about men feeling that women (females of any age) are attractive and cute (parents tend to think their daughter is cute), but in honor of you (and the children's future, meaning that it's irresponsible to the whole family for him to do that), your husband should be focusing his attention ONLY on you (he should also grow up and stop playing games like a teenager, leave that for the mid-life crisis).
If you let this slide, it will just get worse. Nip it in the bud!