I've been reading recently how some sun cream can cause allergic reactions, like eczema, in some people. I head that toddlers in particular can have a reaction to the preservatives that manufactures are obliged to put into products to protect their skin from the sun. Cremes for sensitive skin with a high SPF factor can be expensive. There is though another way, that is to make your own sunscreen. Instructables recently put up an article on how to do this either with a bought creme, or making your own creme in the microwave. So a basic creme might be made up of your favorite oils, some bees wax and the active ingredient. The drawback is a shorter shelf life, but made in small batches this shouldn't be a problem.
There is some evidence that citrus oils should be avoided in cremes, although they will help against sun-burn they may inhibit the skin's ability to repair DNA damage. It is better to make the creme using oils that give some resistance naturally. Zinc Oxide too is the better active ingredient.