Thank you all for the suggestions and comment. I will say that MIL flies once every 2 years or so. she thinks about first as though it's the movies and will be simply jaw dropping.
I have tried to gently explain to her what she will be getting, but I don't think it got through. I had been telling her and FIL that international is where you want to splurge and that I can help with that, but she just really wanted to do this and doesn't like the idea of leaving the country.
There isn't a long layover so lounge access isn't really needed, and their originating airport is small enough to not have a lounge at all, though it is a good idea.
MSPeconomist I really like this idea of creating something myself and maybe looking for an escort for the layover that would be special.