Absolutely go. Children bring light and life and much-needed joy to these situations. We had a wake for my brother last week and all of my children (ages 5-13) as well as my niece (almost age 2) attended the whole four hours. My cousin brought his 3 year old son. A couple of other friends who couldn't get sitters came with a spouse or other friend and had the kids stay in the car while they tagged off on coming in and giving us their well wishes. I told them that their children were welcome to come inside but they insisted that it was easier to just leave the kids in the car with the other adult (the kids weren't dressed, one was napping, one was cranky etc.) so I didn't push it but we wouldn't have minded having them there at all.
My kids have all been to several wakes and/or funerals. They're not traumatic for them at all. They just know that death it a part of life and when someone dies, we show how much we loved them by gathering together in remembrance.