It's doable, but....
I wouldn't go strickly with the 11psi. I'd air 'em down till there was a SIGNIFIGANT bulge in the tires. Every tire and weight combination is different so a blanket statement of 11psi may or may not be best for you.
If possible, follow someone else and see how they are doing.
Stick to the wet sand if possible. I little salt that can be hosed off (do this anyway after being on beach sand) is better then getting buried.
Check the sand for other tracks. If they're deep, you might want to reconsider.
If you've got some old blankets or boards, take 'em with you.
High speed will keep you on top of the sand and get you much further before you get stuck.
Make sure the shovel fits your wifes hands....
Have fun, remember the trip is the adventure, not the destination.