Yep, Margaritaville has plenty of chairs and loungers free of charge.
It's a nice place to hang out for the day, I have done it many times. Plus they have a very americanized menu for the kids
I like it there because the beach is nice, easy access to bathrooms, nice loungers, water trampoline, etc.
I don't care for when they bus in the AI or cruise ship crowds but if you manage to go at a time that doesn't happen it can be a fun place to hang out. They even have a little playground for the kiddies

I second Booger's recommendation for food at Seastar, they have a menu that is sure to please anyone.