We were contracted to revise and modernize a static web site that is very active in terms of adding content but had not been significantly reorganized since the mid-2000's. We are migrating them to a CMS and adding a ton of new functionality, reorganizing the content, etc.
However, we are concerned that just throwing the new site out there upon approval from the client will be a bit shocking to their user base and may generate a fair amount of backlash and complaining on social media which we would like to limit/avoid.
Are there any best practices to guide us in preparing the users to "get over it" or otherwise mitigate hostility to something new?