Based on your stated use, 16^B should probably be enough. What eats up storage is video and photos. Some people here have 16GB of photos alone. However, remember that you can't upgrade the storage on the iPad.
Generally I keep my songs on my iPod 60 GB Classic. Sometimes it's just easier to listen to my favorite music at work through the iPad speakers. I never put music on my iPhone, as I also always carried my iPod.
Photos I just loaded just to play with the various photo features. On the iPhone, I only had a couple of dozen.
I would only sync 1-2 videos to my iPhone, mainly for taking to mom's house and playing on her TV. She doesn't have Blu-Ray and I love the ones that come with a digital copy.
My iPhone is an 8 GB, and even with a lot of apps it wasn't until I loaded on a movie or two that I came close to reaching the limit. My iPad, I just load whatever and not worry about what my limits are for now.
Point is, the 8 GB iPhone limit never bothered me. But on a device where it is so much easier and pleasurable to consume things, I knew I didn't want the 16 GB, so between 32 and 64 I opted for 64. You can very well manage what apps and things you really want loaded on your iPad and 16 may well be enough. But like the previous poster said, you cannot upgrade memory, you can only do more swapping.
Can you please tell me how to enable the iPad as mass storage. So far I have not found any options.
I'd love to use my iPad as external storage.
Also I think you should get the biggest capacity iPad you can afford. You never know when you want to do more staff on the iPad or somebody else in your family stores lots of their staff.
I have 64 and only 10gb left without even thinking 16 is not enough. You'll spend more time messing about worrying about memory usage than you will using the iPad
I bought a 16GB wifi+3G. I have two iPods (16GB and 30GB) so I don't need to put loads of music on my iPad. I normally stream videos from my computer if I want to watch them on the iPad. Majority of the space is used by photos and apps. I am never really in a position where I cannot have remote access to my laptop or files from the ipad so I don't see the space as a constraint.
Personally, I think that unless you plan to put your entire DVD/Music collection onto the iPad, 16 might be enough, 32 maybe if you need a little extra space.
Air Video, best video app ever. I have not tested it using a VPN connection, but in theory if you created one from the computer hosting the Air Video Server tool it should work whereever you are. This is providing you setup the VPN to allow access from outside your home network.