Fashion Tips for the Middle-Aged Man...
No more Tommy Bahama print shirts; one more trip to the Magic Kingdom or Jazz Fest you stop, you look around and every fat man over 40 is sporting a Hawaian shirt from Stein-Mart.
If you're thin, do a polo style shirts with interesting insignia (cue the Daaa Daa Daaa Da!) link. A little heavier, perhaps a 'fishing' shirt, but no big bass or redfish unless you really do fish regularly.
Khaki shorts are good.
As aforeposted, comfort is most important.