You basically just have to ask around. Just ask politely for the senior discount. If they have one, they will give you it, if they don't, well, then they won't. I'm not a senior yet, but I went through the same thing being a student, I found out that some local restaurants give "student" discounts ;) Goodwill Industries theft shop, and a local Wendy's will give student's a 10% off discount. It's really nice, especially in this bad economy.
One of the only ways to find out if they give senior discounts is to ask. Many places do give senior discounts.
You can sometimes find airline discounts for seniors by calling United Airlines to make your reservation. You won't find senior discounts on websites. You have to call.
You can check out different travel agencies in the local yellow pages, or you can find websites that are specialized in senior travel and discounts. There should be many different things for you to choose from and you will find something good for you.
You can find reliable information on senior travel discounts on the following webpage: http://seniorliving.about.com/od/travelsmart/ss/traveldiscount.htm
There are a lot of websites that you can get senior discounts online. There are places like travelocity.com and orbitz.com that offers good prices. Another place that you can go to is www.cheapflights.com/travel-tips/senior-discounts/
The most travel discounts can come from organization like AARP or triple A. These offer bulk national discounts that are most advantageous for senior citizens.
There are airlines that offer discounts to senior citizens but you have to find them. here is a good place to start: http://www.onetravel.com/travel/senior-travel-deals.asp
Many airlines and travel agencies offer discounts to seniors. For some examples on pricing you can visit www.cheapflights.com/travel-tips/senior-discounts/ or www.bargaintravel.com/senior_travel.html
You can find available senior travel discounts on numerous websites. Vacationstogo are extremely credible and offer these discounts. Seniortravel is another good one that is also reliable.
http://www.cheapflights.com/travel-tips/senior-discounts/ Is a good website that might help you find some senior discounts. Just look up a few airplane companies that offer it. Delta Shuttle is an example.
If your grandparents are traveling to Australia this summer, there are good senior citizen airline discounts that they can find through AARP, AAA, or kayak.com.
Many different companies offer senior discounts through programs including, but not limited to aarp. The best thing to do would be to call any travel agency you may be interested in and asking if they offer any senior discounts.