Prepare the kids
It's important to tell kids what to expect from their photoshoot. I like to have parents build excitement around it. Also use my name when describing the photoshoot so that I am not a stranger. Let them know that "My friend Angie, is going to take our pictures and it's going to be so much fun!" or "Angie loves Minecraft or Unicorns or ____________ too!" (Just let me know what they love and I can love it too).
Ask them what they think a fun family pose would be. Maybe they want to spin in circles or jump in the air. How about a silly smile and then a nice smile.
Make sure everyone is feeling their best by being well rested and fed. Plan your photoshoot around nap time and try to make sure they get a good nap as best as you can. I understand that not everything is in your control especially when it comes to kids.
Bring the Snacks
Think of non staining snacks that are quick to eat
Avoid juicy or sticky snacks that get on clothes or take too long to eat
Bring/play an Activity
An activity is a fun way to break the ice with shy kids and get playful pictures. We may or may not use the activity, but it's nice to have when young children are struggling to warm up.
Prepare Yourself
Week before - Have a solid plan for outfits and hairstyles a week before you shoot. Make sure the outfits and shoes fit and are comfortable. Trying to figure out what everyone is wearing 2 days before the shoot is a bit of a struggle. Especially when things don't fit like you were expecting. Give yourself room to make adjustments.
Day of - Leave yourself plenty of time to get ready. I like to add 30 minutes to the time that I think it will take me to get everyone ready. This 30 minute margin can help with hair and wardrobe malfunctions or children meltdowns. You (and your family) will feel a lot more relaxed if no one is rushed or feeling that sense of urgency.