> two elderly women taking a bucket list trip is barely a scratch on the surface compared to other sources of pollution

Unfortunately air flight is very carbon intensive per passenger. One single flight can be equivalent to a person's carbon emissions for an entire year, per passenger. So if they visit 18 countries on 7 continents, for the two of them its possible this trip alone could generate up enough emissions as if they lived for 25 years longer each. Obviously they aren't directly generating it, but they're supporting the business nonetheless. This article itself is promoting air travel.

That said, we currently live in a very fortunate time where its possible to curb your emissions and legitimately offset your emissions. Flying to Europe for example and then taking advantage of the very large high-speed train network only for example. There are also carbon offset companies that directly pay farmers for carbon offset projects, or you could plant some trees yourself, growing large gardens, etc. It will take time but I say they probably have enough time and the means to offset their contribution.