When DD was 10 (so not much older than these boys) I was horrified to watch her scarf down three chicken breasts at a go - and this is a child that was thin and in good shape, not someone with pounds to lose - but she did it daily. breakfast, three eggs, toast, as much bacon as she could finagle me out of, a pastry, and then by lunch she was ready to go at it again. Kids can, and do, need a TON of fuel when they are getting ready for growth spurts.
I'd agree with Cherry to try and either do smaller portions with extras on the table or serve it 'family style' and let the kids get their own servings. If they are eating everything, even when they fill up their own heaping plates, then I'd say they likely are getting ready to shoot up a few inches.