IMO the HP areas pulled off a feat of immersive theming and attention to detail greater even than anything Disney had done previously. They're more comparable to Galaxy's Edge: for a Star Wars fan, that makes a world that they've dreamed of come alive, and every little detail contributes to the world-building. Similarly, in the Harry Potter areas, there are plenty of tiny details to appreciate, and a fan would want not just to race to the rides but to set aside time simply to look and explore.
They can get very busy, and Diagon Alley is very compact, so it gets crowded. It can be nice to go straight to these Harry Potter areas on park opening, or visit them near park closing, to be able to see them with fewer people.
One of the most "magical" experiences is being chosen for the "wand chooses the wizard" ceremony. The first HP book describes Harry buying a wand, trying a few that don't work for him, before finally the wand-master finds just the right one. This is replicated as a small show in the wand shops in USO, with an actor as the wand-master, and one guest being chosen to try the wands. You can enjoy watching, but if your daughter wants to be picked, there are a few things that can help; we tried and got picked!
First of all, the wait for this show can get long. There is more room in the Diagon Alley wand shop than in Hogsmeade, and you might want to "rope drop" this experience, or at least do it earlier in the day.
Second, the wand-master often picks children, and it helps to show that you're a really enthusiastic fan by dressing the part. The Hogwarts robes sold in the park are about $140 (and the wand is expensive enough, around $70), so we bought robes on
Amazon for more like $40, with a white shirt and Gryffindor-colors tie. It's a fun way to enter into the theming anway.
The wand can be used in many places throughout the HP areas, in which you wave the wand in a certain pattern and you can cause something to happen, like a fountain to shoot water or a window display to move. These spots also develop lines as the day goes on, so they can be good to do early.