I would go to whatever travel agency that you like to use and talk to a travel agent. They should be able to provide you with information on senior vacations.
You can find information on Michigan Vacations at the Michigan Organization website. Once on the page, hover over "Plan" and select a menu option to view information on Michigan Vacations, Plan a trip online, learn local info and more.
There is plenty of information out there, including info from friends and family. You can also go to their website, "www.funjet.com", to find out more about their vacation plans.
One can find more information regarding Minneapolis vacations by consulting their travel agent, who would be able to provide information and prices for their client.
Contact a travel agent and they will be more informed of senior travel adventures. I am sure there are many out there, and they will cater to the different activity levels your parents may be looking for.
You can find all the information you need and more on the web. http://www.hostelhandbook.com/budget.htm. Look at this and then make some phone calls.
One can find more information about senior travel on various places across the world wide web such as the Senior Living website and Senior Travel on About Dot Com.
There are many options available on types of vacations and locations, depending on your needs. Here is a great resource for learning a bit more about them and to begin planning your trip: http://www.cheapflights.com/travel-tips/vacations-for-singles/
Many cruise offering companies provide senior discounts. Here are some senior discounts from Carnival Cruises: http://www.cruiseone.com/travel/editorial.jsp/edType/Custom Page/pagename/Carnival_Senior_Specials?. Also, here is some more information on senior discounts for cruises: http://www.cruisecheap.com/cruises/senior-discounts.html
You can visit www.seniorhousingnet.com for more information on senior living facilities.
Find all info on Google
You can find more information about senior transportation online and by looking through your local Yellow Pages. It is also advisable to get some referrals to find more information.
The best deals on Cruise vacations are at http://www.lastminutetravel.com as they are more cheaply priced than Priceline or Travelocity.