It’s nice that your niece-in-law had such a beautiful celebration in the countryside, especially since it involves her good grade in the university. I think it is better to celebrate excellence than mediocre. I'm sure you won't be there if it were the other way round.
The photos of the lilacs are really pretty, and I can imagine how great they smell.
I also understand what you said about sitting quietly. Sometimes, it's just easier to observe, especially when the language is different. I'm sure it because of your in-laws you aren't saying much. If it were to be your family side, they would make you talk.