You’ve got a couple different ways of doing this - it all depends upon how you’re deploying it.
For example, if you’re using nginx as your webserver, you would change the listen directives for each configuration to specify different ports. (Or, you can allow nginx to listen on standard ports and assign the different projects to “directories” within the url structure - that’s how we do it.)
Or if you’re using uwsgi directly, you can specify the ports in your ini file.
(I was going to mention doing it with gunicorn, but gunicorn recommends running gunicorn behind nginx.)
Note: I still recommend getting a domain name. if you’re paying for a static ip on EC2, you’re probably paying more for that than you would for a cheap domain. And if you’re not paying for a static ip, then you’re going to have issues to deal with when you get a different IP address.