Here's a thought: When presenting the AVAST offer, have the install checkbox UNCHECKED (a/k/a Opt-In). If I want AVAST, I'll check it myself. You can even add a 2 second delay for me to read the offer before the "next" button is enabled.
Before, if I accidently installed Chrome, I could easily uninstall it. AVAST is a royal pain to uninstall (if it even uninstalls 100% of the files and registry settings.)