I think the pool may just be as they’re usually fairly cold which little ones tend to really dislike most of the time. The rest just sound like it maybe a little bug. As long as he’s drinking plenty of water and eating something then he should be fine. The good thing about it is that it’s a holiday so you will be home before you know it so don’t worry about not being home. Just keep an eye on him and keep him sheltered from the sun as much as you can to ensure he doesn’t get heatstroke at all x
I understand being anxious, but I’d just keep eye on him, specially his temp. If he’s happy ect it might just be small 24 hour bug. Try keep him hydrated, (take advantage off the free ice lollies if he’ll have them). I think the first holiday especially if they over 1, it can just all be a bit strange and over whelming. I didn’t really enjoy our first holiday, it was all a bit much even for me as it was a new try of holiday x