Virgin Mobile offers the 3 Beyond Talk and 3 payLo plans at this time. There are no family plans.
However, using the Virgin Mobile plans, you could set up your family with a phone and plan that is suitable for each member. Mom and Dad could have the $55 unlimited everything from the Beyond Talk plans and a smart phone or Android phone. The kids could each have a payLo phone with an """"allowance"""" for minutes or messages. $150/month for 2 $55/month Unlimited Minute Beyond Talk plans and 2 $20/month payLo Talk plans. How does that sound? You could even setup Auto Top-Up to automagically pay your plans every month. Prices exclude phones.
Don't forget that Virgin Mobile USA is part of Sprint Nextel.