What do I tell my parents?

My friend and I are going out to the bar on Saturday night. Both of our parents would be fine to drive us and pick us up they've done it before. This weekend though we might not go home we might be staying with our boyfriends. So the dilemma is do we tell our parents were staying at a friends in town and won't be coming home? But then what if we don't end up staying with the guys, then we need to go home but our parents aren't expecting us. Usually we go home around 2:30 but that's a little late to be calling parents with a phonecalls they aren't expecting. Plus both our moms are worry warts so they would assume something bad happened that we needed an emergency ride home. Any ideas how to pull this off? Biggest thing is its not certain we will be staying with our boyfriends cause they may not come out with us