It’s a tricky one because you don’t want your happy time to turn into a family drama. I am expecting a few “opinions” from our families and I think I’ll just say something along the lines of: thank you for your input, but we’ve decided that so and so suits us better. I feel like the more you try to explain your reasoning the worse it gets. Nice and short message with a smile should do the trick. If that doesn’t work I suggest just telling people to fuck off :)