What would you accomplish by accepting their invitation? Yes, you might avoid the embarrassment of turning them down all the time but that would be all. The Bible sets a high standard for God's people: "Avoid every kind of evil" (1 Thessalonians 5:22).
Instead, ask yourself what God wants to accomplish in their lives, and how He might use you to help them. From what you say elsewhere in your letter, they apparently have no interest in God or the church, and their only desire is to live for the moment. But God loves them, and He doesn't want them to keep living such empty and meaningless lives. God loves them so much that He sent His only Son into the world to die for their sins and bring them into His family forever.
Ask God to help you see your neighbors through His eyes, and to have the same love for them that He does. Then ask Him to help you be a witness to them of Christ's love and concern. Let them know you appreciate their invitation, but tell them honestly that this is not the kind of entertainment you wish to pursue.
Then pray for them, and ask God to help you be their friends without compromising your commitment to Christ. And as God gives you opportunity, share with them the good news of Christ's forgiveness and new life.