I'd bubble wrap them each individually, then lay them onto each other, make sure they're snug in the box so they don't shift around. Make sure there's bubble / popcorn between the edge of the box and the edges of your laptops.. keep all sharp objects away.. like the prongs on the power adaptor. Should be good. I write FRAGILE on all sides of my boxes.. and always insure so your covered. Never know..
MacPro 4,1 2009 6 core 3.46 w/BenQ 32" 4K BL3201PH / 980 Gtx TI Amp Extreme
Mac Mini 2006 (kids)
Synology DS1010+ w/ 15TB Raid 5
2x Apple TV 1 160GB w/ crystal HD decoder
Funny story.. I forgot to include it in the big box of iBooks I sent to the buyer, and when I discovered that (almost immediately), I packed it up and mailed it off separately. So, I don't, but I got it from an ehMac member so there should be more out there.