I think you did the right thing OP. How on earth else is your wife going to respect you and value you in the future if you don't lay down the law like this, ignore her feelings and needs and just say **** this for a game of soldiers, I'm off, look after yourself. Your relationship with her will be stronger and, by seeing your example first hand, I reckon her family will come around soon too.
Hang on a minute, that's the wrong way round. Nope, big screw up. Time to apologise and empathise now, and mean it.
NB - do NOT bump off the other parent in order to swiftly demonstrate your newly restored competence at another funeral. This would be a significant strategic mistake. You'll have to wait for nature to run its course.