Are you expecting people to criticize you? If you are familiar with Scratch, then that will save you some time. Game jams are supposed to be fun, and if you have fun with Scratch then go for it.
However, you do need to have a Github repository with your custom code in it by the end of the jam so make sure that you use a tool that works with that requirement. I do not know if the browser-based Scratch tools make exporting the code easy.