as someone who has written webapps in both lisp and python, I would recommend sticking with python. you have to choose the right tool for the job and get comfortable working with different languages. I am a huge fan of CL, but if you go down that road for a webapp, you will spend a lot of time filling in gaps in the framework instead of focusing on the functionality of your app.

Django may be the wrong tool for the job in your case. If so, I recommend exploring some of the more flexible python frameworks like pylons before making the switch to common lisp.