allergy rash and the beach?

[Cheerybigbottom]

Hi all I need some advice

My four year old has contact dermatitis from a suncream allergy, he's on Piriton and the rash is pimply and fading. Worst looking on torso and thighs (areas I never put suncream on lol). The rash is not sore or itchy, but is noticeable,

Neighbour have asked us to go to beach with them today, I wonder if it would be OK? We have a new sunscreen which says suitable for contact dermatitis sufferers and I would not apply it to torso or thighs as he has one of those 2 piece swimsuits.

Four year old really wants to go rock pooling but I'm uhmming and ahhing would it make things worse?