I would do something health/science related that you enjoy. If you enjoy research, go for it. If you never did research before, why not try it to see what it is like. If you are going to take classes to boost your GPA, make sure you do really well cause if you do, it will only help.
I think it's a little bit early to start "playing." You don't want to send the message that you're a lazy bum to the admissions committee. "So, Junella, what are you doing now?" "Uh, I spend most of my day reading and I play tennis every other day." You can do all this stuff AFTER you get in but before that, you have to demonstrate that you have lots of interests, like to stay active (physically AND mentally), you get the picture.