5'9 and 68 kgs

Come here you , I want you in my belly !
Seriously you could ride a Boogie board and get away with it ,
Like DJ says the 10 ft mana will be a fine fit . Having the family involved is a great way to earn good brownie points too.
I have the 11'6 and it would be like paddling an aircraft carrier for you.
All the best with the choice .
Ant