1. Relax! (and don't be afraid to be silly)
I know this is obviously easier said than done, but relax! The best photographs come from you guys just being yourselves, for children this is a lot easier as Harry is showing in the photograph above (he loves dinosaurs - can you tell?). I always thought that part of Sandringham looked a little like a scene out of Jurassic Park, Harry is giving a great example of a dinosaur hiding among the nature.
2. Think of games you play at home
The Simpson Doherty's did a great job at this - I mean look at her happy little face! It's so simple just swinging her around but she absolutely loved it.
To also capture your joy as the parents is just as important, it's sometimes about the moments just after being thrown in the air. I think Ben might have scared himself a bit with how high she went!
Interact with each other, in fact in someways you need to try and forget for a bit that you're even having a photography session and just hang out and have fun.
3. Have a cuddle
Raise your hand if you love a cuddle! (I'm raising mine). It's always best to get nice and close together for photographs, this is an absolute pain if siblings are at that age where they don't want to be anywhere near each other, but that also just shows their personality! You can't force a cuddle it has to come naturally.
This one is a bit more posed, but at least they look happy to be next to each other... even if they maybe didn't want to be ;D
4. Just, be.
If your family are not ones for displaying affection, just be together, walk around and natural opportunities will come for your photographer. Just following a family around is sometimes the best thing to do.
5. If in doubt, throw some leaves in the air!
Other than the love, and amusement coming from family, I've found that throwing leaves in the air is a for-sure way to get children (and even teenagers?!) to smile. This is more autumn/winter specific and a time when if you have a portrait session with me I will more than likely bring a bag full of leaves with me.
I hope that was helpful or at least that you enjoyed taking a look at all the different example photographs I've taken!