Just whipped up this little cocktail with some fresh passionfruit juice my wife made today. Really simple to make. Pint glass full of ice, 1.5 oz of white rum (get good stuff. I like the Malahat Spirits rum), passionfruit juice (or any in-season fresh tropical fruit juice!) till the cups 3/4 full, then top off with seltzer/bubbly water. You can adjust this up and down on the amount of each ingredient as you see fit. Shoot, take the rum out and just have a refreshing drink for you and the kids. But I like to keep it in for after the kids are in bed.
Happy living!
Cheers!