Suggest that your in-laws do the same and refuse to listen to their complaints. Likewise, if you're tempted to confide in your in-laws about your marital or family troubles, know that it will only serve to further miscommunication, perpetuate the problems, and break down the trust between you and your spouse. Always use direct communication. It will lighten any awkward moments and will get your point across in a polite way. Your in-laws will probably appreciate this approach much better, too.
Most people shy away from the idea of having friends over when their in-laws come for a visit.
Having other people around at the same time that your in-laws are there is actually a great idea because it can buffer any kind of tension or awkwardness that either of you feel and it encourages everyone to be on their best behavior. It's almost a surefire way to keep resentments in check and hostilities at a minimum. It also gives you extra emotional support during this stressful time. Every good performance has an intermission. The same is true when you are hosting your in-laws.