If there is one museum in Washington that you should visit, this is it. The HMM is one of the finest museums I have ever visited, both in content and interpretation. Admission to the permanent and traveling exhibitions is free of charge, but if you want to visit the permanent three-floor main exhibit (which you WANT to do), you need to get a ticket with a time indicating entry. You can get these for free the day of, or order ahead of time for a small service fee. This place packs in the visitors, so unless you're visiting in the off-peak season or arrive very very early, there is a strong likelihood your admission time will be in the late afternoon, if at all.
The museum is sympathetic to families with small children, and many of the videos and displays with graphic or violent images are either behind a tall panel or inside a box (where you have to be tall enough to look down into). For as crowded as the museum gets on an average weekday, the timed admission tickets keep a steady flow of movement of visitors. I've been to this museum several times in the past few years, and I notice something new each time. The HMM also has temporary exhibits galleries, so new shows are always being rotated through.
For a topic so intense as the Holocaust, the HMM approaches it in many different ways, none of which I would label as over-the-top or insensitive. It's important to note that the museum not only memorializes those who died but also celebrates the survivors and forces of support during WWII. I commend this amazing museum and encourage everyone to visit at some point.