If the code needs to actually INTERACT with the hotel booking engine(s) you will need server-side code as well.
The fact that Matz and ExcellentCoders did not tell you this means they probably are not the people you are looking for to do the project. I do not know this for a fact, of course, just giving you a warning to watch out.
An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.