Restrict adult content

With Safari you can't. You could get one of the third-party browsers from the store that does have parental controls on it (search for something like 'browser parental') and then hide Safari via Settings > General > Restrictions > Safari 'off'

If you want to keep using Safari you can use a filter service like pageclean.com.

Know any alternatives to PageClean (that works with Safari?) I'd like to use two packages at once.