A single shot of AWS credits in the amount of 75$ or 150$ is way more than anyone would need to participate in this course to the fullest extent 
Hence, if you can get this, I think you are set and we don’t need to worry about getting other people to get us more AWS credits.
To get the most mileage out of your credits going the spot instances route with persistent data might be your best bet - if you want to put in the effort - or if you don’t really care about that you could keep your work backed up on github and spin up spot instances using an AMI (super simple, under 0.25$ per hr).