I think everyone covered on re-hydration. I just wanted to make a suggestion on SPF.

I burley/trailer my daughter a lot and best time to ride is when its not so cold. When heat comes around, I have my hiking hat and shirts.

The shirts are long sleeve button up with UPF +30
The hat is a cowboy style UPF +50

Basically the SPF within the fabric itself. The long sleeve has vented mesh behind the back shoulder to allow air to escape. Works great when riding. And I just apply sunblock on my hands and legs since the hat and shirt covers the rest.

FYI, they have UPF socks, shorts, pants, etc. if you can afford it, get it.