AITA for upgrading my husband's and I's flights on a family vacation?
My husband (M30) and I (F30) went on a cruise abroad with his immediate family. My FIL booked this trip 2 years ago and generously paid for everyone’s flights, cruise fees, hotel rooms, excursions, etc. When we travel with my in-laws, my FIL always pays for my husband, me, my siblings-in-law, and their spouses to fly in economy or economy w/ extra legroom. My FIL and MIL either fly first class or charter private. I want to be clear that I have never, and will never, complain about economy; I always fly economy, apart from a handful of occasions in my life, and I feel grateful to be on these trips and to have such a generous FIL.
This was the first time we did a family trip abroad. For this particular trip, I had the points and money to upgrade my husband and me from Comfort+ (which my FIL booked us on with my siblings-in-law) to Delta One (the flat-bed seats). My husband is a tall man with back issues, had never flown in flat-bed seats before, and the flights were 10+ hours each, so I wanted to surprise him with this upgrade. I didn’t think it would offend anyone given my FIL and MIL were also in Delta One, this was a one-time special upgrade, and my siblings-in-law are all adults and with their spouses in Comfort+, so no concerns of splitting up the family.
Also, my BIL and his wife had a baby 10 mths prior and, despite my FIL asking them to reconsider, they decided to come on the trip and bring baby with them. None of us had kids when the trip was booked 2 years ago, so the itinerary and cruise line were not baby-friendly. I had already intended to upgrade us before their pregnancy, but their decision to bring their baby solidified my decision to upgrade (although I’d never say that). My husband and I are prioritizing travel before we have kids, so we wouldn't have enjoyed sitting beside a crying baby on every flight. As much as we love baby, the entire mood of the trip was altered. It was no longer the relaxing and adventurous vacation we had envisioned and the trip used up all of our vacation days. Sitting in the lounge and plane was the only time we didn't hear crying.
Our upgrade has caused some tension from my BIL’s wife and my MIL towards me. My MIL told my husband that first class isn't for "kids" (referring to us 30 y/os), that sitting in economy w/ the siblings makes for great memories, and "who is going to help with the baby?" (if we wanted to take care of kids while traveling then we wouldn't wait to have kids ourselves). I want to give my BIL's wife grace given that she's postpartum, but she spent the trip "whispering" to my MIL, side-eyeing me, will interrupt anytime someone asks me a question, and is extra bubbly with others but flat towards my husband and I. My husband can’t tell if his brother is offended. My FIL was surprised but not offended; he doesn’t like surprises, so I should have told him ahead of time. I truly did not think this would cause issues, but maybe I'm not as sensitive as I should be?