I do the sound at the "Harbour Stage" for the 'Scottish Traditional Boats Festival' every summer (it's held in a small town called Portsoy in the North-East of Scotland - 4th & 5th July this year if you want to come along) and I've never really found the iPad hard to see outside - what I have found is that you need something to hold the iPad 'about your person' between acts, when you're getting the next act on stage and set up - in the general melee I tend to forget where I've laid it down - or it could get stood on - or worse.
I've been searching for some sort of harness - without success thus far (unless someone on here knows different) - so I use a home made shoulder bag - brightly coloured so it's easy to spot if I do lay it down somewhere.
And knowing how unpredictable the British weather can be something waterproof could be a good investment as well....
The plus side to all this is that I can sit, at a table, outside the pub, down at the lovely old harbour in Portsoy and mix the gig from there - it's a hard life sometimes....
http://www.stbfportsoy.com/