Normally, I'm against taking the tough stuff out of the Bible when you tell stories to kids. I will happily talk to the children about the fact that Jesus was crucified, that he did actually die, and it was hard, because if you tell only the happy stuff there's no dramatic tension. I will happily talk to the children about the second half of Jonah, when Jonah acts like a complete selfish brat outside Ninevah and has to have a talking-to from God. I will include the fact that Pharaoh ordered that every male child born to the Hebrews be thrown into the river, when I'm telling the story of Moses. The suffering of God's people is part of the story, and without that part, all we have is a namby-pamby "God loves you and everything is always happy and wonderful," which kids know is a lie.
There are, however, some edits I will make. And it's often a difficult tightrope, and I don't think I always get it right. But I try to ask the questions: is this part crucial to the purpose of the story? If so, I include it. If it is, but it's still difficult (e.g. Potiphar's wife is crucial to the Joseph story, the rape of Tamar is crucial to the story of David and Absalom), then I will gloss over the age-inappropriate details.
For example, when telling the story of Joseph, I will say, "Potiphar's wife told lies about Joseph, and he was thrown in jail." This accomplishes the same purpose as the original narrative - she was treacherous, and jealous, and had him thrown unjustly in prison, as is crucial to the story - without finding myself in the awkward position of explaining to children what "filing a false report of rape" means.
And for David and Absalom, I will tell the children that "after Amnon hurt Tamar, Absalom became angry, and he killed Amnon." This still gets you to the narrative place you need to me - Absalom was in the right, Amnon in the wrong, but his response was possibly excessive, and, either way, the death of a son grieved David, leading to Absalom's exile and growing resentment.
In the story of Noah, I use the Beulah Land script, which includes the line "Noah and his family and all the animals" - the "two of each kind" in the original can be considered synecdoche, in which a part of something stands in for the whole. The style is clearly that of a folktale. If a child asks "what happened to all the other people who weren't in the ark?" I will say, "what do you think happened?" and they'll generally come up with an answer that's satisfactory to them. But it doesn't usually come up. The people who weren't on the ark stand in for "evil" - not "evil people," but "evil in the world" in the story, and children are usually fine with that. I do avoid dwelling on the sufferings of the drowned - that's not the point of the story, the Biblical writer doesn't even mention them, and it takes away from the purpose of the narrative, which is one of salvation and covenant, not punishment. Children may decide that God had another way of saving all the other people who were good, or they may decide that all those people were bad and it's okay for them to die, just like it's okay for the witch in Hansel and Gretel to be shoved into the oven. The Noah story is full of archetypes and folktale elements; it's not a modern realistic novel, and shouldn't be read as such.
So don't shy away from a story just because there are elements that are difficult - the Bible is full of sex and violence, and there are ways of telling these stories that keep the dramatic tension of the story to children without leading to questions like "Daddy, what's incest?" after the Sunday service!