The best airport to fly into is Lambert Saint Louis International Airport. There are many options for hotels and airbnb rentals along Interstate 70, as well as in Old Town St. Charles.
Hotel
Holiday Inn St. Louis Arpt West-Earth City, an IHG Hotel
3400 Rider Trail South Earth City, MO 63045 (314) 291-6800
Hotel
Drury Plaza Hotel St. Louis St. Charles
380 Mulholland Drive Saint Charles, MO 63303 (636) 724-5772