Has anyone made a long haul trip with a 3 month old?

Here’s the thing

My MIL got it in her head that she wants to invite all the family to travel to Denmark at the last week of June 2025, before her mom passes away so she (the grandma)can meet the country of her ancestors (my MILs mom is 3rd gen Danish)

By that time, our baby will barely be 3 months old. For us it will be wintertime (we live in South America) and Denmark will be starting summertime.

I’m having concerns regarding the plane ride and I have no idea about traveling with a baby

I’m afraid I’ll be all stressed out and won’t be able to enjoy the trip

My husband does not want to go if I don’t go (since he doesn’t want to leave me alone for 2 weeks with a 3 month old) and I don’t want him to miss out on the opportunity

I’m also worried I’ll be missing out on my students (I work part time as a private tutor), and June is peak exam/testing season, so if I go I’ll miss out on a big part of my income for the month

I’m conflicted and I don’t know what to do

Also I don’t want to make a 15hour flight with my baby on my lap

Anyone has any thoughts?