I use AWS heavily but for simple projects like this I prefer Heroku. And thats because you have a bit of back office. Without that part I'd use some of static web hostings. Deployment is really simple (i prefer Git push).
If AWS is a requirement, for this I think I'd use static S3 hosting for React app (I assume its client side) and connect it to AWS Lambda & AWS SES for that simple emailing in back office