LBK:
As far as I am aware, this halacha of aveilus for the children of parents who are sitting shiva r”l, only applies when the children are in the same town as the shiva. This is out of respect for the parent who is in mourning, that they act appropriatly and not enjoying life as if nothing happened.
This is known as “Misablin imoy”
PL”B: Ask a competent Rov for a final p’sak.
To all in CR: We should always share simchos with each other!