When my Dad passed away in 06, my li'l guy(Michael) just turned 4, he was really close with his Pappy. My Dad had been sick all of Michael's life, so he knew this day would come. It was hard to tell him the night he passed. Michael was so brave, but he knew Pappy was happy in heaven. I explained to him that we could say goodbye to Pappy, and that we would see him in his "heaven bed", I didn't think he would understand casket.
He would look like he was sleeping, but his soul was in heaven.
When we got there, Michael went right up to Pappy, he pulled a chair up up the casket and stood there at his side for an hour. I didn't interfere and when he was ready he touched my Dad on the face and said goodbye sweet Pappy, then got off his chair and put it back.  For the rest of the viewing, he stayed near the back of the room and greeted the family and friends, and came to check on me from time to time.
He was such a trooper. He did ask all the questions that come up, and I answered them honestly, he had had no ill effects from going, but I believe he would have never let me live it down had I left him home.
We go to the cemetery often and bring flowers,  or have a donut with Pappy, which was his favorite thing to do with Pappy! He dreams of him and tells me Pappy is so happy with Jesus! 
So I believe if Your daughter wants to go you should let her, and if she gets restless, have someone take her into another room and keep her busy.
We also tag team, with other family members and help keep each others kids in another room while paying our respects. That works well for us, and if the kids want to see the family member they have a chance, and also some family member to keep them company.
I'm sorry for your loss,
                                  Brenda