iOS is generally considered to be "simpler" and more user-friendly than Android, easier for the computer illiterate.
USB socket & SD slot... Important IMO to consider whether they are actually needed in the first place, not simply whether they are present or not. USB, SD card, and HDMI adaptors can be purchased if necessary (just like for the Android powered Samsung Galaxy Tab 10.1 which also has no card slot or HDMI

), but would someone who is computer illiterate want or need those features? Best to find out what they actually would want to do.
As for Flash itself... again, it may not be present, but will it actually be needed anyway? Flash is not required for BBC iPlayer, ITV Player, 4oD, Demand Five, YouTube, Sky/BBC/C4 news, or streaming live Freeview TV... All of those have apps available, and some also work via the browser thanks to HTML5 sites. If the potential user in question wants to use those and various other video sites which have moved on from Flash or offer an alternative, then the lack of Flash is not an issue. It's only really a sticking point if you play a lot of browser games which use Flash, as of course those will not work.
Battery... Not much of an issue IMO. If it dies during the warranty period (unlikely), it will be fixed by Apple. If it dies after that, then Apple will fix it for a fee. Not as simple as swapping it out yourself, but it's not something that happens quickly. It would take some time for the battery to eventually give out.
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Re. iTunes -
As freeview_user said, iOS devices no longer need to be connected to a computer running iTunes to set them up.
All iPad 2s should come with iOS5. When you first turn them on, they ask if you want to activate wirelessly or wired, so you can go through the whole set up without connecting it to a computer and without using iTunes.
You can also update the software and perform backups wirelessly and without using iTunes.
Apps, books, videos, and music can all be downloaded directly to the iPad itself using the relevant apps on the iPad.
You would only need to connect it to a computer an use iTunes if you wanted to transfer your own content to it (e.g. your own CDs or videos).