Boys will be boys - like herding cats but you can't beat candid and natural moments
You don't have to apologise for your children not following instructions or sitting still and posing perfectly for the camera - that just isn't going to happen. Just embrace it, run with it, see what they do and be quick to capture.
I spent the morning with these boys, all cousins from three families and it was chaos but it was great; They couldn't sit still no matter how hard everyone tried. But sometimes that makes for fun photos, candid memories of kids being kids - playing, exploring, completely oblivious to the camera.
I have young children myself so I know what it's like; don't be embarrassed, don't apologise, don't worry - I've got this.