In Canada there is an "Off" bug spray for kids that I have used on my guys when they were small. I have also used a deet-free spray which I am sorry I can't remember the name of right now. Have a look to see if you have a similar product there. You do have to be careful on how often you use it on them, and make sure you spray it on your hands first and rub it in well. I did not use any product on their faces as I was afraid they would rub some onto their hands and later into their mouths. Depending on the temperature, maybe just smoothing it onto their clothes will help and you won't have to worry (of course, if they are not wearing much....). I have read about how great bounce sheets are in the pockets, and that would be more child friendly...
Good luck and enjoy! Annette