What Lens for Luggability?

For best image quality both indoors and out the Panasonic 12-35mm F2.8 lens is the most versatile.  It also has onboard image stabilization (OIS).  This is a must for Panasonic cameras when shooting at slow shutter speeds.  Olympus supports in-body image stabilization (IBIS) so OIS is not important.

If you are looking for a lens that will give you both wide angle and super zoom capabilities, then I would go for the Olympus 14-150mm f4.0 - 5.6.  While it's not very fast, it covers 99% of the shots you are most likely to take.  It does not have on-board image stabilization so if that is important to you then you should look at the Panasonic 14-140.  It has similar optical characteristics and also supports OIS.

Enjoy your new camera and have a great vacation!