Christina,
Manfred has this issue cracked but for more complicated edits similar to this you can use more than one layer and use different heads from different pictures. Simply make a selection from one image, copy and paste it onto a new layer in the main image and follow Manfred's instructions above. You can then manipulate the angles and position of these selections using the Move and Transform tools.
A good tip I learned quite a few years ago when taking group shots, was to get them all to close their eyes before the shot. Then say "OPEN!" when you're ready to take the shot. Doesn't always work but it is always a laugh.
Also there is ALWAYS one person that will be allergic to flash and therefore every time your finger goes near the camera they will shut their eyes. So always take more than one shot. Take five or six at least until this culprit can be identified. Then give them a pair of matchsticks.
![Big Grin](https://cdn.cambridgeincolour.com/forums/images/smilies2/biggrin.png)