A full century of life is something to be both happily celebrated and sincerely commemorated. Gifts for someone who is 100 years old should honour her life, bring her closer to loved ones and communicate your admiration and affection for her.
Give the birthday boy a month full of outings. Take him to every grandchild's sporting event or recital, to church on Sundays, to visit friends and out to dinner at his favourite restaurant. Or, gather your family and take a birthday trip together. Take the birthday lady to the beach and let her enjoy a week or so with her family. You could also pay for her and her spouse or friends to take a relaxing boat ride to watch the sunset. Ask if there is anywhere she has always wanted to go, and then try to make it happen.
Food and Drink
Treat him to a week of culinary delights (check for dietary restrictions first). Cook for him at his house one night, then order Chinese food another. Let him pick the food and you make it happen. You could also create a different food-and-drink gift basket for every day of his birthday week. Day one could be sweets (sugar-free, if necessary); day two, fresh bread; day three, cheeses; day four, a variety of imported international fare; day five, fruits and vegetables; day six, his favourite beverages, and day seven, fresh deli meats.
A long life deserves comfort in the twilight years. Install heated flooring in the birthday lady's bedroom so she'll have warm feet in the winter months. Or, buy her a mattress pad and heated blanket. You could also buy her a power chair to get around more easily or install a new bathtub with a small door for easy access. If she has chronic aches and pains, hire a professional masseuse to visit her home once a week during her birthday month to gently massage the trouble spots.
If his heart can take it, throw him a surprise birthday party with old friends, coworkers and your entire family. Take plenty of pictures and put them in an album for him. Or, consider a symbolic gift, such as planting a tree in his honour or making a charitable donation to his favourite foundation. You could also have a boys-only family party and share a bottle of his favourite whiskey and his favourite guilty-pleasure food. Afterward, take him on a memory road trip. Visit important sites from his life and listen to all his stories.