Mick
IMHO it very much depends where the canal is and what the neighbourhood watch scene is like in the area. Locking the boat to something solid would be worthwhile and it will help you sleep better too.
In some places where there is a fair bit of passing traffic there is a lot of potential to have things be stolen. In some canals the residents are proactive and make it plain and obvious to visiting boats that they have been photographed and their rego numbers and the peoples picture are kept for latter reference if any need arises.
Dogs that are yarded close to the boat also work well as the sound of upset dogs and sensor lights are also effective.
In your case as your only there for a short time you will probably be OK, time will tell. Take your dog and bed it down close to the boat!
Have a good long week end and enjoy yourselves.
Cheers
Chimo