Help me setup the network at my workplace

[Noufas]

So, I work at a restaurant. It's in an old building in london, there is a basement with an office and as you can imagine, thick stone walls.
We have 3 wired ticket printers on a router, and we have a dsl connection.

My boss's brother works for belkin/linksys so he asked me to find any equipment from these 2 companies in order to setup the wifi to be strong, and provide customer wifi if it's possible.

Any recommendations? Cost can be not an issue, but lets not get things for the sake of getting them, but for the sake of practicality.

 

[Noufas]

The thing is that this will be provided for free by the company. That's why the linksys/belkin requirement.
Guest wifi is not a priority, the kitchen printers and the wifi being up is the main issue.
Orcvader: the restaurant is in two rooms, with a narrow corridor connecting them, and the kitchen being in the middle of these 2 rooms, with walls on all sides.
The router is in the main room/bar and iirc has 1 more ethernet port left.
I will see about running cable to the basement.