There are no rules. Do the decorations how you want or in what way works for your family.What is important is that you keep Advent. Is it better not to put up decorations and spend your Advent as the decoration police or putting up decorations and keeping the sacred mysteries of the Incarnation and our redemption always before you? If people are worried that you have a tree up, chances are their faith is about as real as a plastic tree.
Maybe for Lent you should give up listening to morons with no authority.