Absolutely. My kids come home ravenous so there's no way they would even get past 3.30 pm without having had a decent snack of fruit and something else. I can perhaps understand not having actual dinner depending on what sort of time the other family usually has dinner - if your DS was originally going to be collected from your house at 6pm that's possibly a lot earlier than the other family eats - but no way would a child in my care be allowed to go hungry.