Not that easy I'm afraid. There's more of them every year. People living in conditions where they need to fight to survive don't have time to worry about the survival of others, which means those who can't survive on their own or provide some benefit to others generally don't get any help.
So sure - fixing their situation would be the best! Please come help! We desperately need more real help here.
But barring people jumping on planes to come and help, which from experience doesn't seem to happen terribly often, it's better for these children to be able to survive.
My point is: you're doing this the wrong way around. First you fix their situation, and then you make child labour and sex tourism illegal. If you do it the other way around, you're just hurting people. You're just condemning children who had no other choice to survive to having no means of survival. Sorry to say it, but it's reality.
EDIT: To put it in a more clear example: a village is eating disgusting looking seaweed that tastes horrible because there is no other food nearby. You think nobody should have to eat this seaweed, so you make eating this seaweed illegal so that they can't eat it and offend you. End result? They starve because you didn't provide them with better food before making seaweed illegal.