These are a bit easier if you know what to look for, but frankly they are the one I make the most mistakes with by far, for whatever reason. Initially, you want to look for any clear damage. Not just scratches but more like bruises or anything moldy or mushy. If it is already growing something, you can simply put it down.
Next is to examine the skin color. If there is still green color present, you probably want to wait on it. You want something that is in the beige, tan color range with a slight hint of green, that’s good. Too much green means not ripe, too pale and soft means most likely overripe.
Weight matters as well. Pick up a few melons and see which one feels heavier than you expected. Generally, the heavier ones have more juicy flesh, maybe they are just tightly packed, who knows. Whereas lightweight cantaloupes are usually dry, and dry cantaloupe is the saddest type of cantaloupe.
Okay, so now you flip and press the bottom, where the blossom end was. You do not need too much pressure. If it gives a little this is probably what you want to see. If it’s too soft? Like your thumb leaves an indent? This is probably soft and mushy on the inside.
And finally, yes you should smell it. Like a pineapple, the nose knows. A cantaloupe that smells faintly sweet is probably at peak ripeness, but if it smells too strong or stanky-bad in that overly sweet sense, it may be going bad. If it smells like melon liqueur? Avoid it.
So, I guess that is sort of the short version of what to examine with these fruits. Like I said, it is not rocket science, but once you have learned to recognize a couple of little things, like how it smells, how it feels, what kind of weird scarring it has, you will get better at getting some good ones. This obviously won’t guarantee your kid is going to love fruit, but at least when they agree to take a bite, you won’t be handing them a complete dud.