Unfortunately, I have heard many times in the past, that the more adults there are in a group outside by/near a pool, the more likely it is that a child may die. I know that at first glance that sounds counterintuitive, but the explanation is, that everyone thinks that with so many adults present, a vulnerable child will be watched at all times, and therefore completely safe. In reality, the opposite is very sadly often true, because everyone else thinks that someone else will be watching the child..
Also, although I don't want to sound like a party proper, no one should have any alcohol to drink until after the younger children are safely in bed, and with no chance of them being able to leave their room, and possibly escape to the swimming pool. I would not go on that sort of holiday unless at least 2 adults agree every day, to not drink alcohol at all on the day that they are in charge.
I'm not saying not to go, but if you are your child's only parent who will be there OP, then you are going to have to stay on high alert throughout the whole holiday. When Grandparents, or adult cousins, etc, offer to be in charge of a child, they are almost certainly telling the truth, or they think that they are, and very sadly all sorts of - maybe unexpected - distractions can occur. A horrible example of this has been reported on, in France as it happened, several times this last week. If so many parents can somehow manage to forget that they have tragically left their child locked up in their family car, outside in the blazing hot sunshine, then what real expectation can there be that a group of close family members, relaxing on holiday, and not believing that one day it could be one of their young beloved family members who ends up paying such a terrible price.
Please NB I was only using France as a tragic example, as it has sadly had at least 2 young children die in hot cars over the last week. But of course that also happens in nearly every country over the years: especially ones that are not used to such extremely hot weather! Some of those places include; the UK, parts of the USA, probably Canada, and almost certainly most of the other Northern European Countries.