8" Windows 8.1 Tablets to replace XP desktop at my Dads business?

Hi guys, I'm writing here to help out my Dad. He and my Mom run a small business by themselves and they've been using the same desktop they got 8 or 9 years ago. It's so slow that Skype calls are lagging and youtube videos freeze at 360p if we don't use the HTML5 player.

The main software they use is Skype, Word, Excel, Web surfing (YouTube etc) and some specialized Windows only software so their new PC has to be Windows x86.

Now that XP support is coming to an end I brought up the suggestion that they replace their main desktop with a tablet.

I'm not to clued up on Windows tablets so could you help me out here!

The price range we are looking at is around $250 which means you can get the Dell Venue Pro 8, Lenovo Miix 2 8 or the Toshiba Encore 8 - the ASUS is a little out of their price. The Encore is quite a bit bulkier than the other two but has a HDMI port, I was thinking of using Miracast anyway so unless there is any other reason to go for it I'm leaning towards the Venue Pro 8 or Miix 2 8.

Any thoughts?