Lock Screen too big to see swipe, so we can't 'open'!

The screen saver is showing - but about 10 times normal size, with the result that we can't see or use the swipe action. We have tried re-booting (holding down start and home buttons, etc) but this does not resolve the problem. Looks like she may have inadvertently increased the screen size and then allowed the iPad to lock. It's my friend's iPad (90-yr old lady who got the it from her grandson) and she can't remember her Apple ID or anything so we haven't been able to contact Apple direct for advice on this. We realise we may have to contact grandson and get him to make trip to Apple store - he lives distance - not sure he has access - yikes! So just in case this is simple to resolve any help would be appreciated.