Locating a hotel (or two) that's convenient and affordable for your out-of-town guests is a common courtesy; you can pass this along using an insert card. You needn't include all the features; just give the basic room rate, plus contact information.
Providing specific travel information to the city itself is generally not necessary. Airline information and road atlases will help people figure out their own travel plans.
If you want to avoid this enclosure all together, you can include all this information on your website. A grandparent who is not online can get theirs from you directly.