I have been there once, 10 years ago, so my information is outdated, but anyway...
Expect a small provincial airport (similar to what you would find in any US city of 100 thousand inhabitants). Maintenance and general conditions should be OK, but don't expect new-like appearance. Services (immigration, baggabe pickup, currency exchange, ground tranportation) will be basic but functional and rather efficient. People will be friendly and most of them will be reasonably competent in what they are doing.
You will probably see few airplanes, most of them MD-80's, A-320 and maybe an old 727. You will probably see some small private or corporate airplanes, some of them rather old (a kind of air taxi), maybe one or two new.
Better concentrate on the beautiful beaches than the airport. Have fun and enjoy your vacations in Ixtapa-Zihuatanejo. Mexican beaches are one of the best in the world, the tourism industry infrastructure is very good, so I am sure that you will have good time.