I suppose if you have the client run the installer themselves and check the box agreeing to the EULA it's "legal"ish to put AVG on there. Just can't do it for them.
So it isn't legal to install any software on the client's behalf? Don't techs do this all the time? Most software has an EULA. Some customer's bring a new computer with software (e.g. bought from an appliance store) and ask for it to be set up with username, updates, software, data transfer, email setup. This involves the tech agreeing to many EULAs on the client's behalf.