Wireless is the easiest option and is what most travellers expect these days.
I have WAPs bridged together around my B&B to give wireless access in all the rooms. In addition I have a couple of RJ45 sockets in seating areas for the few that can't do wireless or the odd Mac that won't play nice with the house system.
You should think about creating a separate IP group for the hotel guest side. The owner is probably not going to want guests having access to his machines.
Some interesting reading here:
https://www.grc.com/nat/nat.htm
I'd suggest cabling across to the hotel side and going wireless from there.