How to prevent hug of death on EC2 Instance?
If you want something quick to get this sorted without much more knowledge I'd recommend elastic beanstalk. It's another AWS application which will handle the load balancer configuration and instance scaling for you.

There's no extra cost on top of the load balancer and instances so you can keep using t2 type instances but let elastic beanstalk scale as much as you want to help.

Auto scaling isn't instant and in times of spiking traffic will take a short amount of time, minutes normally, to be able to handle a spike but it will be much better than manually scaling the instance size and is really easy to get to grips with.