It is wonderful that you are keeping that family baking tradition alive. Raisins are classic in muffins because they provide concentrated sweetness and chew without adding excess moisture to the batter, but you have quite a few affordable and accessible pantry alternatives that will not alter your baking time or batter consistency.
First, diced fresh apples or pears are among the most economical substitutes. If you have an apple sitting in your fruit bowl that is slightly past its prime for fresh snacking, peel it and dice it into small, raisin-sized pieces (about a quarter of an inch). Because apples have a firmer cell structure than soft fruits, they hold their shape during a standard 20 to 25 minute bake and release moisture slowly, mimicking the chew of dried fruit without making the crumb soggy.
Second, other dried fruits or dried fruit odds-and-ends work seamlessly on a 1:1 volume basis. Chopped dried dates, prunes, dried cranberries, or dried apricots can be diced to the size of raisins. If you only have a few leftover pieces from previous recipes, you can combine whatever odds and ends you have in the cupboard. If the dried fruit feels particularly hard or dry, let it sit in warm tap water for five minutes and pat it completely dry with a kitchen towel before folding it into the batter.
Third, thoroughly drained canned fruit is another budget-friendly option. Canned peaches, pears, or crushed pineapple work nicely if you drain them in a fine mesh sieve and press out the excess liquid with the back of a spoon. Once chopped small and patted dry, they blend into standard muffin batters easily.
Finally, if you want a change of texture rather than fruitiness, pantry staples like sunflower seeds or rolled oats offer great results at a low cost. You can toast rolled oats in a dry skillet with a tiny pinch of cinnamon and fold half a cup directly into your dry ingredients to add heartiness and a gentle nutty flavor without changing your baking temperature or timing.
