Power factor correction for LED lighting on a generator
A LED itself is resitance load, while the problem is the rectifier and step down circuit. The cheapest LED lamps use a series capacitor that uses its reactance to increase overall impedance, which means that such lamp will have a cap. phase lag not the inductive as motors or lamps with ballasts.

http://www.ebay.com/gds/LED-Lamps-using-5050-LED-chips-/10000000177064387/g.html

Or the LED lamp can have a small SMPS inside with a transformer, in this situation you will get more a harmonic distortion rather than phase lagging. You should buy one of these first, then see with power meter.  

Lastly, LED lamps consume less power than incandescent lamps, so you will have extra current reserve for feeding also the reactive power.
IMO you don't need nothing at all, perhaps a choke or sinusfilter.