I would ask the homeowner/company what the setup is. direct pool access from the house? separate gated fence?
How obedient are your kids? Rule followers or not so much? Are they used to the "never go near water w/o an adult"rule? ie- you have your own pool and its not an issue normally? Depending on the answers, I would consider putting in those alarms - the watch alarm or the thing that floats and beeps if something falls in.
Not to be overly paranoid, but this is EXACTLY the sort of situation where lapses happen. There are so many adults everyone thinks someone else is watching the child and they slip off.
dd1 10/05
dd2 11/09
and ... a mini poodle!