First, wherever possible, I try to use a 12VDC charger for as much as I can. That eliminates loss due to inefficiency in an inverter. Look at the OUTPUT voltages of the power supply/charger units. If they say 12-14VDC, you can run the device directly off the 12VDC system with a cord from Radio Shack.
I also generally prefer to use a DC to DC converter supply for the laptop. I got ours from Dell, but if you have an expensive laptop, I'd consider a quality 12VDC power supply from Lind Electronics
The INPUT wattage of the laptop power supply and other chargers is usually printed on them, but sometimes instead there is an INPUT amperage at 120VAC. Multiply the input amperage times 120 to get the watts.
Cheaper inverters output what they call, "modified sine wave." In my opinion, it should be called "modified square wave," since it's wave form is a stair step, rather than a smooth sine wave. This can cause inductive things like motors and transformers, especially in "wall wart" power supplies to run hotter. For many things, the extra heat isn't a problem, but for some it is, and can shorten their life.
True sine wave inverters are much more expensive, but could be cheaper than replacing chargers for some equipment.
Don't forget that with inverters, the amperage coming out of the batteries is roughly 12 times that being fed to the 120VAC appliance. Running at it's maximum output, a 100W inveter can take two fully charged 100 amp-hour batteries down to 50% charge in 10 hours.
Something else to consider is that the 12VDC cigarette lighter outlets in the Winegard antenna plates are only rated at 8 amps
. That's what an 80W inverter will draw at full output. Exceed that and you could damage (melt) them. Any larger inverter should be hardwired into the 12VDC system, preferably as close to the batteries as possible. Long wire runs from the batteries to the factory lighter outlets can drop enough voltage to make the inverter give a low voltage warning.
Just some thoughts...