I am presently teaching my wife to sail on a 16 as well as JamieZX, though my 14 experience is limited to college (a LONG
). Our weight tops out at +- 300lbs and we find the typical late morning and early afternoon wind outside of the Marina Del Rey harbor (about 10-15kn on a good day) to be perfect for learning and having fun.
Based on your stated maximum combined crew weight and the fact that you're teaching the kids, I think a 16 would be a better choice (I'm a US Sailing Level I instructor, so I have a sort-of informed opinion). It's got the jib and main sailplan which will be much more common on dinghies or other boats they might sail, it's faster with more people on it, keeping things educational and fun at the same time, it's got a better racing/support class (if that's even a remote future possibility) and there seems to be lots more learning liturature on the 16s (probably as a result of the class structure) than on the 14s.
Downsides are that it can be difficult for a kid(s) to right after it goes over, and kids love to tip them over, and they can be heavy for kids to put in and take out of the water.
These comments disregard cost, your sailing environment, etc, and the fact that you have access to a 14 right now, and, all things considered, the 14 might be a place to start with a 16 down the road at some time. My two cents, anyway. Good Luck with whatever you choose to do