Child, Kid
The child radical and the child kanji are exactly the same.
So, if you know your radicals, you know your kanji as well! This won't last forever (where radicals are exactly the same as the kanji) so enjoy it while the kanji are still small and simple!
し, す
こ
None
To remember the sounds し and す we'll use these mnemonics: There is a child standing in front of you. You look closely at the child but something seems wrong. You rub your eyes and when you open them again there is a sheep (し) in a suit (す) in front of you. You yelp, blink, and it's back to being a child. Are... all children really just sheep in suits?!
The child runs away and you chase after it. Every time it's about to turn a corner it looks like a sheep in a suit again, but whenever you yell and point, it turns back. You're the only one who can see this sheep suit child!!