Check the menus on allears before you get too worried. I would be very surprised if most 7 year olds wouldn't be satisfied with a child's TS appetizer plus meal plus dessert. If you're worried about it - do all buffets - then you can all eat as much as you'd like.
And for CS...if the 7 year old is still hungry afterward - a snack credit could be used for something 'extra' at the end of a meal - a dessert, some fruit, some fries....I would think that should be enough.
I was a little worried with all the recent Child's plan changes, so I went and actually mapped out all/most of our meals. Now I'm not worried at all. For TS: my kids are having: pasta at Tony's(large portion from what I remember), shrimp or chicken with rice at Teppanyaki, burger or canyon skillet at WCC, and 3 buffets. For CS - it is a little more limited - but you can still find options - mine are eating burger, pizza, burrito, turkey sub, grilled chicken wrap and the occasional nugget

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Unless they have changed portion sizes, I would be VERY surprised if two kids meals is not equal to or more food than one adult sized meal. So, if your main concern is size of portions, I'm thinking you'll still end up way ahead if you order each of your little ones their own kids meal - ESPECIALLY if in the past you ordered one adult meal and had 3 kids splitting it - I'm certain the kids meal size is larger than a third of an adult meal.
So just try studying the menus and hopefully it will set your mind at ease.