B.M.
I am sorry for the losses your daughter has experienced. It certainly is a lot in a short period of time expecially to such a young child. My husband is a funeral director, so I might have a different perspective on this than others. The decision to take your daughter to the funeral depends on her. Explain to her what she will see, (people crying, talking about the deceased, the flowers, the room, the casket, and if it will be open or not) then talk to her about it. Tell her it is OK to cry, but more importantly, it is OK to laugh too. People often feel bad or disrespectful if they laugh at such a sad time, but it is a tribute to the deceased that there are good memories.
I would suggest taking her, but allow her to decide how far to go. She may not want to go into the viewing room, just reassure her that it is OK, and be prepared for someone to take her home if she becomes too upset or decides the whole thing is too much. Some funeral homes have "children rooms" with books, toys and TVs. I would suggest contacting the funeral home ahead of time to see if they have a room for her and the other children attending.
Books, as suggested by other mothers, are good and will help her you discuss how she is feeling. Some funeral homes have people trained to deal with grief on staff, and can suggest books on the topic that would be age appropriate. They may even have books to lend to you.
Death is a part of life. You do not want to over emphasize that with her, but because it has been such a focus lately, try to talk about it with her when she wants to. If you are religious, put it in those terms. Remind her of the lives each person lived, and try to take some of the focus off of the death, but always let her know it is normal and ok to be sad.
Hope this helps.