Turtle turtle

Back story : there's a woman who knows ben (erin's boyfriend).  She is a therapist on the west coast writing a children's book - one of the characters is an anxious turtle, wearing a swimsuit, of course.  I'm struggling trying to (visually) develop his character, and these are my rough first sketches from last night.  First of all, I'd LOOOOOVE feedback, artistically.  Second of all, I'll be asking the author these questions, as well, but here are my main unknowns :

1.  Is his shell supposed to look like a backpack?  Because with a kid, you expect that.  But if his whole body is supposed to fit inside, that could be a problem.
2.  How do I make swim trunks look like swimwear, not boxers?
3.  Do turtles (specifically this one..) have hands?  fingers?
4.  Toes?
5.  What does anxious look like vs. sad or sullen?

Help! :)