Can you charge two 7.4 lipo's wired together as a 4s 14.8 or will this kill them?

Don't think it will kill them just watch it doesn't hurt your charger and that you are balancing them.

You can wire them together and charge 2 2S lipos as a 4S. The dicey part is balancing all 4 cells. To do this cleanly, you need to balance them together also. That means making a balancing harness that puts the balance taps together.

Here's a good how to with plenty of explanation -

http://www.rc-monster.com/forum/showthread.php?t=9881