Which is safer, spot on flea treatment or tablet?

I have to give my cat flea and worming treatments every few months, but I was just wondering which is safer for my kids (9, 15, 17) because I think the treatments are flea treatments so I am worried that if my kids stroke the cats they will get pesticide on them ( I know you ae supoosed to wait for it to dry, but even theen there must be some of the product still on).