Seating

So I’ve seen signs that’s state “We are family once the knot is tied, so pick a seat not a side” which is a fabulous idea for us because the majority of the people at my wedding will be my fiancé’s family. So I am going to do that but would it make much sense then to have assigned seating for the reception!?? Because then people who shouldn’t sit together might get stuck sitting at the same table. Please help!