Lost in the Language Labyrinth

So, I got a message about work – someone saying they needed more time to complete something for me and would I mind waiting a little longer – and so I was about to send a message back saying ‘sure.  Take all the time you need.’  But then I thought, wait… what if they read as if I’m being sarcastic?  So in their mind it goes ‘sure… take all the time you need.  It’s not like we’re paying you for this, you useless ****sucking ****ard…’ which is not what I meant to imply at all.

Should I put in a smiley face?  Should I write that I’m not being sarcastic?  Or would that come across as patronising and even more sarcastic?  I shouldn’t do that, but maybe I should write a few more paragraphs in my message reiterating and therefore making it abundantly clear I’m not being sarcastic.  But I’ll have to think very carefully about the wording…

By the time I’d figured all that out, they’d finished and so the problem had resolved itself.  At least it was a productive day for someone.