If their aversion to food has got zero to do with their knowledge of the variety of food available, and what hard work cooking is. Also wether or not their mom cooked for them, then has nothing to do with manners and politeness. IF, I'm right, then I'm really sorry, bcoz your summer will be stressful as you're setting yourself up for failure. Think about it logically, what 'normal' teenager turns down junk food, or WANTS to eat bread, butter and crackers, even after you offer him lasagne? Really? They're not even a TINY bit curious? Even if their mum didn't cook much, doesn't mean they know nothing about food, or that that would explain their behaviour, I'd expect them to be curious about what they were deprived of and or jump on the opportunity to have something better! Think about it, they've NEVER seen or HEARD, about other food? Really? NEVER been intrigued to try it, coz they weren't cooked for?? Makes no sense... Once again, goodluck for your summer.