If your clients websites aren’t mobile responsive they may well be. After a lot of speculation and rumours, Google has now stated that from April 21st being ‘mobile friendly’ will improve a website’s rankings.
“Starting April 21, we will be expanding our use of mobile-friendliness as a ranking signal. This change will affect mobile searches in all languages worldwide and will have a significant impact in our search results”. Source: Google Webmaster Central – http://bit.ly/1MdOqbO