Too many showers?

Hello, I have a situation and I'm not sure how to handle it! My parents are divorced and my mom and my step mom were adamant about not having the showers together. Fine. Then I have a small group of friends throwing me a shower. Now my sister in law tipped me off that my mother in law is throwing me a fourth shower. How do I politely decline having this shower? I honestly don't have enough friends and family to come to three showers, four would be WAY over the top. I was really hoping for just one big one but didn't want to get in anyone's way. I don't know how to politely decline this since I'm not even officially supposed to know. Help! I hope I don't sound ungrateful. Definitely not the case!