Making kids smile in photos has been a challenge for photographers since the beginning of portraiture! First things first. Know their names. Get their ages and names and preferably photos of them before your shoot so you can memorize them. Sometimes it’s hard to keep it straight with 5 or more kids at a shoot!
When you meet them at the shoot, don’t start shooting right away. Get down and introduce yourself and talk a bit. I always talk about what they’ve seen on their trip so far and what their favorite experience has been on Maui. Then start shooting while they are still clean. Keep them away from the water or dirt until the end of the shoot. Start with the posed images, then switch to some nicely lit jumping shots when they start to fidget, then silly faces, then a perfect giggly smile, then a tickle fest with the folks or sister, then go to the natural light candids.
I have them run towards the water then back again. I get little ones on dads shoulders. I have mom raise baby up and wiggle them up high (if they’re neck is strong enough of course). I also have fun props. Squeeky toys, lens animal scrunchies, or funny bobbly antenna headbands are all great ideas. Have the mom or dad stand right at your shoulder and make googley faces.
For older kids, ask if they are involved in any sports or gymnastics. Have them do what they know and enjoy. Like back flips, handstands, air guitar, soccer kick, ballet moves, exploring the lava rocks, anything to get them moving. Movement brings about natural smiles. All the active shots should be interspersed with some still, relaxed regular shots too. Make sure to photograph what mom wants.
Above all else, work fast and get the shot while the expression is there. Always have your finger on the trigger!