No! Towels and chairs, yes but palapas on the beach are public and first come first serve.
Yes, do it 3 days prior to leaving! Check the website below! https://www.aruba.com/us/plan-your-visit/getting-to-aruba/online-ed-card
On a Saturday, it is recommended to be there 3 hours early! On a weekday, 2 hours early!