I can perfectly do this for you. I will be using SVG image edit with Raphael js to achieve what you are looking for. Using SVG and Raphael will make work way lot easier and simpler.
Relevant Skills and Experience
PHP/MySQL, jQuery, Raphael, SVG
Tbl_layout (id, name, svg, status) svgtext stores all image info
tbl_layout_tables (id, layout, identifier, name, status)
tbl_chairs(id, tableid,identifier,name,guest)
Proposed Milestones
$50 USD - Develop an ui to add the tables to the image. You can drag drop to position it / 3 days
$100 USD - I will be saving the design to database so you can edit it in future too / 2 days
$30 USD - Mechanism of adding/editing the guest names to the chair / 2 days
$20 USD - Testing and deploy / 3 days
Additional Services Offered
$1 USD - After work service for couple more days for free as support on new issues findings if any
What is the purpose of "unlock" and "lock" buttons in the top right compartment of the image?