i used to keep a RES. Funny thing, how can such a small little turtle grow up to be a monster and eat anything in its path... kids sure do grow.
I personally think you only need the UV light(its also a basking light) and skip the night light.
I kept my 5 inch RES in a 29 gallon tank, cant say it did as well in a huge tank but as long as it can swim a little and has a decent basking area for it, it should do fine.
You do not need to keep any substrate if you do not want to, i used river rock, the larger rocks the size of sliver dollars so its crap wont be stuck inbetween rocks and it wouldnt so hard to clean either. I used a Fuval plus 2, i wish i had a magnum at that time.
I used to use 2 bricks to hold the drift wood so the turtle could bask in the light like this | |, it was simple and easy to clean.
i dont know if you do this to clean your filters and water. But i used Rubber gloves to handle anything in the turtle tank because its filthy, smelly and it carries a lot of bacteria and it can also carry samonella(mispell), i dont want to tell you how to run things but i would not let your daughter touch the turtle
hope this helps