Hopefully someone else will be able to advise you regarding sprays for children but I never travel without Anthisan cream which is excelent for taking the itch out and helping healing if you do get bitten.

We were in Tunisia last June, don't recall many mosquito bites, but we have used the repellent with deet in (sold in most supermarkets) I take a jiff lemon (strange I know haha) but been told to put a dab of lemon on all your pulses, as they don't like it, and so far so good the past few years me or my son have not been bit