Great point friend, I meant to touch on this!
If a sea star is what you and your family really want, I'd encourage you to do some real research, so as not to disappoint your kids. Arguably, the easiest, least expensive and maybe hardiest real sea star is the Chocolate Chip Star (
Protoreaster nodosus), but these animals are not safe around corals if you aspire to also have corals.
Furthermore, many of the sand-sifting sea stars really require a very deep and mature sand bed, or they simply deplete their food source, and slowly starve to death in many home aquaria.
Not true sea stars according to the taxonomists who do this work, but I think bristle stars (a common name with multiple Genera) and the like will make your daughter very happy, and be a much better "resident" in your tank:
Hash tag, not my picture :)
As always, good luck!