My husband cheated on me and left?

me and my 6 year old son for the entire summer to live with his 24 year old girlfriend. I need to seek revenge, how do I do it...any ideas brewing out there. I need something real good that would make them start bickering...the honeymoon stage is coming to the end(as it ALWAYS does)and I need something that will put them both over the edge. thanks in advance :)