When I buy the family membership,can I use it right away at both the parks? Do I need to request free tickets or just show the membership card at the entrance for free admission

Can be purchased and used right away.The only restrictions I see is if you are purchasing ticket online it has to be at least 1 day in advance.

+1 for Nan's response

You should be able to purchase and use family membership right away

You can also purchase tickets, then use those towards the cost of the membership. Holding members get cards, with guest tickets - depending on membership level.

You can just show the card at entrance for regular entry. Some special exhibits/shows require ticket(s).

You can use it right away. Done it a couple years in a row.

I agree with Nan and Arindam