There's a number of points I'm wondering:

- Was it impossible to clean the sheets? Hotel sheets are usually bleached and depending on the colors used, they may have just come off.
- What exactly had to be exchanged? What is the cost for the replacement?
- How old were the replaced sheets? You wouldn't have to pay the full price of new sheets if the damaged ones were already old. You will usually only have to cover the current market value.
- Why are the pictures black and white?
- If the sheets are replaced, I would ask to receive the old sheets.

I certainly don't see a difference between the "accident" of spilling juice and the children coloring the sheets. Accusing the children of a "deliberate act" is a bit over the top. In both cases other people's property got damaged.

HTB.