I'm not a fan of vow renewal either. (Or, 'vowel' renewal as one autocorrect put it on a PP)
I always thought it was for people who had gone to the brink of divorce but pulled back just in time. I didn't realise it had been, 'bastardised' to get out of an awkward, marriage threatening situation i.e. adultery.
My mum's response, when a friend of hers renewed her vows, was to mime sticking her fingers down her throat ! Most unusual for her to do that. It wasn't made clear why they were renewing their vows. No body asked why.
Someone else who got married just got humoured by the guests attending, who weren't asked for presents but a donation to a goodwill project, should they wish to.
I just cringed through the whole thing keeping my mouth shut and my opinions to myself. Not least listening to them say their own written-by-themselves vows in a great big barn of a little used/deconsecrated church. Was the person that re-married them their marriage guidance counsellor ? If so they had no jurisdiction. The marriage register does not get signed again. So good job it was all a bit of pointless fakery, really.
As my husband pointed out, they (or anyone) is no more married than they were first time round.
The cheeky fuckers of the OP won't need to get double divorced when their marriage ends just because they renewed their vows.
The suggestion to donate to Relate really made me smile.
I understand people renewing their vows so they can have a proper party etc this time round if their wedding day either didn't go as planned was just plain disastrous.
However using it to cover up problems is public papering over of cracks.
(I would love to go to Las Vegas to renew our wedding vows for our silver wedding anniversary but I cba doing all the organising.)