As noted in the question.

A dry cleaning business that has been in operation for over 100 years. Due to change in traffic and poor management, the facility (two locations) has lost about 1/4 of its business over the last 2 years.

What are some traditional and perhaps non traditional ideas for marketing, cross selling, or business partnerships that you have seen or may consider effective.

Expand target market. Use social medias for advertising. Give some eye-catchy promotions for the regular clients so they can spread the word.

A great website. Advertising blitz, and a few nice contacts with bigger clients.

It is so unhappy to see established businesses to go through dark phases. But here’s my recommendation. Take the world's changes and developments as a helping tool to your business.

Today, a lot of people are already using online platforms such as social media. Try advertising your business through it. Social media can reach a larger market because of the scope of people who uses it. Just make sure that you are able to use and manage it well. Try different ways of advertising offered by these different social media platforms. Also Locate the most suitable platform for the type of business you have.

Adding some innovation and keeping up with the trend can help in sustaining your business. Try doing market research to know the demands and needs of your target customers. Also changing or remodelling business strategy can also sometimes be helpful.