I can only tell you that I went to my grandfather's funeral when I was 11yrs old and it had a lasting and negative impact on me. I was scared of my parents dying, my animals etc. I couldn't sleep without nightmares and I felt so sad for so long.
The finality really really hit me.
I felt the innocence of my childhood was lost that day, and it never came back.
Yes children need to learn the facts of life, of course, but they can do so when they are older it does not need to be when they are young.
It is a huge and upsetting, emotionally charged moment, that is bound to hurt and upset them.
I would let them play in the gardens and then come to the wake. Children at a wake always lighten the mood, and bring joy, and they will enjoy eating sandwiches and meeting relatives.
I am so sorry for your loss, but think carefully before taking them is my only advice.