I was thinking similar to asteffes. First, you already have an Optima Red Top which is good. A jumpstart/boostbox is a great low cost backup. Costco has a very high amp version for cheap and they are always great to have. I keep one in my truck with me all winter to help boost other cars.
If you don't have the power inverter yet, try and find one that has a low battery cutoff. The one I have won't let the battery drop below a certain point. Nice safety feature.
For the laptop, I would actually suggest a different route than an inverter. Using one you are basically going DC to AC to DC. Since the inverter uses power itself, it's better to get a cig lighter adapter for the laptop instead. They are very readily available and not expensive - just make sure the one you buy works with your laptop before buying it (especially if you buy online).
One thing worried me is when you mentioned mixer... Those draw high watts from an inverter. I actually fried my wifes Braun handheld mixer a few years back because the inverter didn't put out enough watts. It was enough to turn the motor, but it burned it out in a few minutes. At least it died making a margarita! So check the wattage rating of the mixer and if you don't have enough watts in the invertor, don't use it. The required watts should be listed on the unit itself somewhere.
/ -- \ Pete Hartl - VE6PGH - 0VRLAND
EXPEDITION = (Encounters + Adventures + Experiences) x YOU