Being in the IT industry for a number of years, I've been somewhat forced to compile a "SHTF Computer Kit." A kit I can rely on when I need access to data at a moments notice, or need to diagnose servers, networks, PCs, etc. My advice to you would be the following:
1. Get yourself a laptop, any size or shape will do, as long as you can carry it when you need it. I would stay away from the "rugged" laptops, as they can be very expensive to maintain and/or repair. As long as you're not tossing it around or using it in a constant downpour, it will continue to function. That being said, if you're set on a rugged laptop, go for the Panasonic Toughbook brand...as they have been around longer than most.
2. Obtain numerous ways to power your laptop. AC/DC/Solar...whatever you think you may need.
3. Make copies of everything you need to keep the laptop running the way you like. This includes the operating system, DRIVERS, office applications, media players, ripping/burning software, document readers, etc. I recommend free apps like OpenOffice, VLC Media Player, CDBurnerXP, Adobe Reader. Also make sure to stay up to date on frameworks such as Java, .NET, Flash.
4. Keep your data on an encrypted external hard drive, save your laptops hard drive space for applications and application data. Be sure to duplicate everything from #3 on the external hard drive as well. Most modern external hard drives lock the heads when turned off so you won't scratch the platter and destroy your data. You will be able to plug this into most computers you encounter, should something happen to your primary laptop. Keep it neat and organized.
5. Make sure your laptop has various ways to connect to the network/Internet. This includes network cables (CAT6 RJ45), telephone cables (RJ11), built-in wireless capabilities (802.11b/g/n), or aircards (USB/ExpressCard/PCMCIA). Many people forget to include a 56k modem on their notebooks, don't. You may find yourself in a place where you have no other choice than to dial-up the the network/Internet. Keep software for dial-up (AOL, NetZero, Earthlink, etc) on hand just in case.
6. Use TrueCrypt for data encryption. It's free, and as close to Government grade as you're going to get. Just make sure you know how to use it, and don't forget your password.
7. Keep the peripherals to a minimum. I have a small wired laser mouse simply because it's easier to use than any trackpad. You may wish to keep a few USB flash drives for yourself and your family as well. I like the Corsiar Survivor series.
8. Get a comfortable laptop bag that holds all of this. In fact, as soon as you bring it home, load it up and carry it for a few days. You'll know if it's a keeper or not.
You've made a great decision to archive your personal data, something which most people neglect to do. Don't forget to scan some family photos as well. I hope this info has helped. If you have any other questions, feel free to ask.
-45JHP