I bought an easy-to-carry booster for my grandson when we went in November. He was 4 (almost 5) and on the small side. It folded up into such a small package I could fit it in my purse. We tried it out a few times before the trip and it worked fine. There were videos to show you just how to use it and it was pretty easy, both in my car and in the Uber we used to and from the airport. I learned about it from posters here on Dis, and I think it may have been the MiFold but I'm not sure now (my daughter has it). Both Bubble Bum and the one I got were rated highly for ease of use and portability.
The one thing you don't get with the one I bought (not sure about Bubble Bum) is an elevated view. It sits pretty flat on the seat, so you kid won't see much. Since we were only traveling to/from the airport, we didn't care. It was awesome to just click and unclick the seatbelt and be able to carry it around easily in a purse or bag.