Windows 8 ASUS Transformer Book T100
Why? Productivity and size.
For the past year or so, the computing market has been moving towards "hybrid" devices. These are devices that cross the line between tablet and laptop. Hybrids tend be Windows 8 devices with both a touchscreen and a keyboard, but some may fold from laptop to tablet mode, and some may detach from their keyboards completely.
The ASUS Transformer Book T100 is the latter, and for its price, it's pretty amazing. Normally $400 for the 64GB version (recommended), it has gone on sale for as low as $300, and tends to hover around $380. For basically a 10" tablet running full Windows 8.1 (as opposed to the crippled Windows 8 RT), and includes a detachable, hardshell keyboard dock (for laptop mode), it's a really great price.
Before you get too excited, be aware that the maximum built-in storage on this device is 64GB, which means you probably won't be storing all of your music, photos, and videos on the Transformer (all of your documents should fit, though). There is a MicroSD slot to expand your storage. Also, 10 inches makes for a large tablet, but a tiny laptop. You might be pumping out an Excel spreadsheet on the Transformer, but you might be squinting at the screen the whole time. However, there is a micro HDMI port for connecting to an external monitor.
Google Android Nexus 7 (2013)
Why? Price, openness.
If all you want is a tablet for entertainment purposes, Google's Nexus 7 Android tablet might be for you. You can some work done, but not like a full Windows 8 tablet/laptop hybrid like the ASUS Transformer.
The Nexus 7 certainly beats any tablet here on price. The MSRP is $280, but more often than not, you can find this tablet on Amazon at a significant discount. Currently, you can purchase the 32GB Nexus 7 for only $5 more than its 16GB variant. Bizarre, right? Last year's model currently goes for $180 (and it even briefly dipped to $100 just recently), and isn't a bad option if you don't mind the lack of a rear-facing camera.
Android OS is known for its openness, which is both a good and bad thing. On one hand, you can install apps (like emulators for playing Nintendo games) from outside Google's app store, but it also means that it's open to potential viruses. Android users are often in the situation of installing antivirus software on their phones!
Android devices are favorites among geeks for these reasons. If you're not a technophile, you may have an easier time in Apple's walled garden where you have less choices and settings, but an easier, more secure experience.
Apple iOS iPad mini with Retina Display
Why? Apps, build quality, speed, interoperability.
Between the three tablets here, at $400 for 16GB, you're paying the most and getting the least for your money. You're only getting a quarter of the storage that the ASUS Transformer provides without the keyboard, and the Nexus 7 has twice the storage for almost half the cost. The Retina option on the iPad means smaller, denser pixels which, in turn, means crisper graphics and better legibility. It adds $100 to the cost, but it's a must.
So why buy an iPad? One answer is apps. Developers tend to create apps for the iPad first because there is less OS fragmentation, less piracy, and more profitability.
Some other reasons why you might choose Apple are build quality, hardware specifications, and interoperability. The quality of Apple devices is impeccable. The only plastic on an iPad is the home button. Everything else is aluminum and glass. Apple's current hardware, their A7X chip, is faster than any quad-core chip you'll find in other mobile devices despite it only being dual-core. Finally, the interoperability of Apple devices is a major draw if you decide to jump head-on into the Apple ecosystem. Your iPad can mirror to your TV with an AppleTV. All of your Apple devices can sync your data (and photos) between each other with iCloud and Photo Stream. If already have a Mac desktop or laptop (or even an iPhone), keep going. Trust me. The more Apple products you adopt, the better they work together.
...Your kids don't really need to go to college anyway.
$380, 64GB - Amazon.com
$400, 64GB - MSRP
For people who want to get real work done while being as portable as possible. Entertainment is secondary.
$230, 32GB - Amazon.com
$280, 32GB - MSRP
For people who just want a good tablet for the lowest cost. Entertainment is a priority. Comfortable with Android OS.