One of the best things I've done to help myself in lesson planning is to make a list of games/activities that I've used in class. I actually started doing this my first year teaching at a hagwon and I've been adding onto it every year since. Usually, I can look at a topic in the book and come up with a few activities or games that will work with the material. But, if I'm at a loss, I just open up the document (in Google Docs) and quickly scan down the list to see what will work. Often, I find something perfect that has been long forgotten.
If you don't already make a list like this, I suggest starting! It's perfect for things like camps where you see the same group for an outrageous amount of time (like 40 hours over 2 weeks!) and don't want to repeat things.