I am sorry for your loss.
I think that as she has asked to see him, after checking with your lovely funeral director on the day that it's still a wise thing, as they will say honestly what they think is right for her based upon their experience, don't restrict it to looking at a wooden box, allow her to see and have her moment with him as she wishes.
I was always kept away from such things, whether for humans or for pets. I was then very scared and, yes, very fixated upon death and disappearing, as that's what happened - death meant being taken away and disappearing, followed by an awkward half hour in a crematorium or chapel and then nothing.
Then I saw somebody in the process of dying and later, their body. It took all the fear away, because I saw the light leave their eyes and leave behind a body; it made sense in a way that walking away - or being prevented from seeing, hearing or knowing anything - didn't. It meant I could stay for a beloved pet to give them a small sense of something safe around them as their pain faded into nothing. It meant that I could be with my brother in his last moments when everybody was saying 'oh no, I couldn't possibly bear to see that'. It meant that the pain of loss was tempered by the acceptance that it had happened in the first place, rather than incredulity and doubt and denial.
I still felt deep sadness, of course, but there wasn't any confusion or feeling excluded/distant/isolated. In a way, it was comforting to know that what remained wasn't the same as what was there at the moment of death.
I would have been able to cope at 11/12 without a doubt. Perhaps it is relevant that I am also Autistic, perhaps not.
Let your DD and the funeral director decide what is best for her. And you decide what is best for you - you have a different relationship with your father, so you naturally have a different experience; whatever that is, of course that's fine for you, it's whatever you need - but do please allow her to find what is right for her.