400 words is not a long page, so I wouldn't worry too much to be honest. If you want separate sections for adults and kids, you could put anchor links at the top, so for example "If you're a parent, here's where you need to be" or whatever.
I use anchor links a lot for long / very lengthy pages - but by "long" I mean around 2,000 words and by "very lengthy" I'm talking about over 4,000. You can see what I mean on this page: [Domain Private]
- the callout box which starts "This is a long page"...
Actually it's one of my shorter pages, at 2,116 words!
Otherwise yes, use the code that Bonnie has linked to.