Some fun ideas for a birthday party for a 70-year-old include having a picture slide show in a "then and now" format and having a roast for the person of honor. A roast can include a best friend getting up in front of guests and sharing stories.
Another idea is to have a space set up for photo opportunities. Hosts can set up a background with a scene and have fun items for guests to wear nearby. The photos can then be collected later to give to the guest of honor as mementos.
It is also fun to create a playlist of the guest of honor's favorite songs to play during the party.