COCO put together an excellent tool to help you look at the various events
http://vegas-poker-schedule.com
You can isolate most of the factors (except time of levels) and zero in on the options available to you. As a fellow Sr I am playing these 4 Sr events during my stay ( I am personally mixing in other open events ) but a lot just depends on your time frame and budget - The RIO WSOP are hard to top if you don't mind the relative small starting stacks
15th June 10:00 17:55 Rio $1,000 WSOP Senior Event - $1000 - 50years+ 98 2018-06-17 senior
16th June 10:00 16:35 Planet H. $600 Seniors NLH - $600 $200k 68 - senior
17th June 10:00 17:55 Rio $1,000 WSOP Super Senior Event - $1000 - 60years+ 98 2018-06-19 senior
22th June 11:00 15:50 Orleans $400 NLHE SPT Senior (50y+) National Championship - $400 - 1A 77 2018-06-24 senior