OpenDNS does not have a product named "Family Friendly", though they do have FamilyShield.
If some computers on your network are using "standard" OpenDNS using a dashboard configuration, and some on your network are instead pointed to the FamilyShield addresses those computers will use both the more restrictive FamilyShield settings (which cannot be whitelisted in any way) plus whatever whitelist and blacklist settings you've specified in your dashboard (except of course your whitelist settings won't apply to annoying blocked by FamilyShield).
If you want this computer to have different DNS filtering settings from the rest of the computers you'll need to make sure that that the computer a) uses a different DNS service entirely (while also making sure that your router isn't somehow directing all DNS traffic to OpenDNS or b) subscribe to one of the paid OpenDNS services, such as Umbrella that would allow you to specify different filtering settings for each computer or c) use a Netgear Router with LPC (Live Parental Controls) which allows ways for individual users to bypass some or all of the DNS filtering.
