One way to do this is to up the age of the star. But from what I understand, red giants aren't simulated perfectly yet. If you up the sun's age by a few billion years and put the timewarp on, say, a few million years a second, you will see it expanding and cooling no doubt.
However, the problem right now is that yes, it expands, but it hardly expands to 100 times its radius that a red giant star is theoretically able to do. It will not gobble up the inner planets like our real-life models predict it will. Like I said, it's not perfect, but the devs are working on new stellar evolution models that should address this.
And I think showing your daughter such a game would make for a great experience. She may not understand everything behind its physics, but I grew up fascinated by the workings of space not though understanding how it works—I still don't today—but through just how massive and beautiful it was.