Just wanted to add my feedback on how things went.
We just got back from UK, Belgium, and the Netherlands. All family members had iPhones.
The Airalo eSIM worked flawlessly using the hints from the group. Pro tip: Activate BEFORE you leave for your trip and download the app so you can track your data. I got the 5 GB plan over 30 days, and it was total overkill. We used it to surf the web, do Google Maps to navigate walks, buy tickets, etc. and we had over 3 GB of data left over.
BIG PROBLEM HOWEVER:
The Airalo is a "data-only" eSIM. So you will not be able to make phone calls to a standard phone. This got us into trouble in two ways:
1) Trying to call restaurants, museums, and tourist sites will be impossible unless you get your hotel concierge to call for you. Some of the hotels we stayed at didn't even have a real land line, they just used their personal cell phones. This was a problem because restaurants were so booked they all needed reservations unless we wanted to get a "grab-and-go" thing
2) We got a credit card fraud alert during our stay sent to our email, but in order to call the credit card company, we needed to call them, but we were unable to do so for the same reason as #1 above. Not surprisingly, there are no more pay phones anywhere, so we couldn't even call on their collect line
BOTTOM LINE:
Next time I will probably research data plus calling SIM cards as a more practical option