Best combination of ec2 instance Family and instance type for large user based PHP application

I have gone through the amazon documentation about instance families and instance types before selecting it, but still i am confused Neither i found related question on any platform. Here is my scenario:

I am in process of developing Cricket WorldCup application which will have thousands of users in first week after it launches. Lets say 50,000 (can go to 100000) users at one time on website. I want to select right instance family and right instance type for that as i will not have time to scale up if site goes down in the middle.

Can anyone suggest best combination? I am using Drupal CMS to develop this application if it will help suggesting right combination.