Just have something int he sponsor letter stating what the plans, if any, are, even if they are vague...
"we'd like to get married in our local church and will discuss this with a vicar when my fiancee gets to the UK".
"we have spoken to the registrar and know we can't book anything until my fiancee gets here, but ideally we will marry in May".
"we are still arguing about final details, as I want to marry in my mum's back garden and my fiancee wants to marry on the centre circle at Barnet Football Club. We have agreed on a spring wedding, probably April, but nothing else yet" (an almost direct quote from one of my clients in interview a few years ago.)
Anything to show you have discussed it.
Vicky