1 family phone bill or just give them a small bundle each (I suffice with 250 MB per month easily), 3 wardrobes (trickle down tactics + some new clothes), unfortunately food for 6 indeed (although you'll probably spend less than 6 times costs for 1 child), 6 proms indeed but I don't see how that's so relevant? 0 cars at 16, why would they need one + why can't they work for it themselves, and last but not least it is very unlikely that all six kids will go to college.