Frequent hand washing (of course particularly after using the toilet), regular (daily) bathing/washing of hair and general hygiene measures to ensure re-infection does not occur is strongly advisable. In particular, the child's fingernails should be cut short and attention paid to cleaning under them. Change of underwear morning and night, pyjamas and bed linen daily, is a good idea. For additional assurance use spirit based or insecticidal cleaner on all door handles, toilet surfaces, etc. in order to eliminate possible deposits of eggs transferred to/from hands, clothing, etc. Otherwise not a great deal to do, the medicine should have cleared out the family's digestive tracts within a week (for good measure). After that keep vigilant, the source is likely to have been from outside the home (e.g. an infested child or else eggs on some surface or other) and reinfection from the same source may occur. If you have a pet you have serious difficulty in eliminating that possible source without getting rid of it altogether. You can google lots of info, this is one such source
http://parasitecleanse.com/pinworms.htm