Yes I can help you to update your client's van website with responsive design that satisfy google responsive website guidelines and work well in mobile devices.
Now kindly share your client's existing website so that I can review and get a clear idea about the total scope of the job.
I have very good experience in website designing and development using WordPress, PHP, MySQL, Ajax, HTML5, CSS3, bootstrap, jQuery, JavaScript etc..
I can give you very good design and well coded responsive works. Website will be W3C validated, cross browser capabilities and well developed.
Lets discuss more details..
Regards
Esha