As others have said - some rain, hot short bursts.
PestoMonster pic looks like it was taken in the Caribbean?
It will rain in Cornwall too, but only if you are on holiday there, like it did when I went, only a few days of course. I do love it though.
Joking aside, you may get some rain where ever you go, I think this is true? My sis lives in Spain which has had weeks of intermittent heavy rain and thunder storms over April and May. Whereas it's lovely here in north west today and we've only had 1 day of rain in about 2.5 weeks. Weather forecast here was for heavy rain today, no sign of it yet, blustery but clear.
Are you still reading? Anyway back to the op by Willow.
I wish I were a weather girl who could guarantee the weather, but you can't predict the weather anywhere, you just have to go with historic trends. And many folk travel happily throughout the year to the Caribbean with no sight of any rain. Would it put me off going there at the time you ask? No it wouldn't.
You just have to ask yourself "Is your holiday going to be ruined if you don't have 100% sunshine, every waking minute?" Is that what a family holiday means, or is it spending time and doing stuff together in a nice place that you'd like to visit.
I have to go and cut the grass now.