criminals are generally pretty lazy and wouldn't take the time, or have the skill, to go out and tamper with a cache. But if this is a concern, avoid no-see caches.
Get a good Topographic Map program, buy a multi-scale protractor, and manually plot your points in either UTM or MGRS. You can use this as a reference when you are actually out on the terrain. Being able to interpret a topo map is money in the bank.
Personally, I would avoid it. Put yourself in the shoes of the family and think of a bunch of hikers putting stuff on your family members grave site, even if it is an old abandoned cemetary. If it feels like a bad idea, it probably is.
The laptop would take some logitical planning, but it would be fairly easy to do. I have my Garmin 76 mounted on the left side of my dash below the side vent(it's a 94 toyota truck-visual reference for toyota owners). I have the power supply coming from my cigarette lighter; tucking the excess wiring below my steering column. The location of the GPS is important. You want to make sure you have plenty of daylight hitting the antenna.
Here's a great link:
http://www.ram-mount.com/
BTW, Doug and Linda: That is freakin HIGH SPEED!! Very Cool Hummer interior!