OK, for argument's sake, let's discuss the minimalist options first.
The most minimal guest list is Thomas and I... This is unlikely to be popular! Marcel is already bouncing around mentally ordering food and teasing Charlotte about female attire. I doubt the parents would be overly pleased either.
So the minimal is probably me, Thomas, Marcel, Charlotte, Léon, Anna, mum, dad, Derek, Amanda, Gordy, Brita, Peter, Miriam, Bjørn, Felix, Theodor and Ursula.
Given this is all our immediate family, we tried to imagine the day.
We'd need to get married on a Saturday to allow the foreigners to get here. Saturday services at Registry Offices are usually 10am-1pm. So say we are married by 1-30pm in Glasgow. What do we do with the rest of the day? We could go to Derek and Amanda's for a quick glass of bubbly as it is in the same street at the Registry Office. What would we do from 2-30pm onwards, say 3pm onwards if you take a photo or two. We could arrange a nice meal in the evening but with just 10 adults, you can't have it in a venue dedicated just to you, so I guess it'd mean a restaurant surrounded by other people. That might last 6pm to 8pm. I presume given 8 kids you wouldn't want to start eating at 8pm... Also you'd stand out as a wedding party so it'd be odd in a normal restaurant. But would this feel any different from a family birthday meal or every other Boxing Day meal? And then at 8pm - what do you do? Go back home and put on the dishes, do some washing? How do you make it a special day? How do you make it interesting for the foreign guests, and the kids and us?
Ho hum :-(