On one hand, eating grapes and raisins is certainly far better than eating candy!! At least the sugar is natural. Still, eat these in moderation if you're aiming to lose weight.
Most of us know what grapes are. They are small berries that grow on vines. Some types of grapes are great to eat raw. Other types of grapes do better when mashed up into wine. Some grapes are great when made into non-alcoholic grape juice.
Grapes are naturally full of sugar. That is how you make wine - the yeast eats the sugar and turns it into alcohol. If you eat a cup of standard green grapes, that is 15g of carbs there.
This might be worth it if they were nutritional powerhouses like some other berries are. However, they are pretty inept in providing anything to you. You get 2% of your Vitamin A, 6% of your Vitamin C, and pretty much nothing else. You'd do much better eating pretty much any other vegetable or berry that exists.
How about grape juice? It's even worse, as with most juices. When they make a juice, they remove the fiber and leave you just with sweet, flavored sugar water. A cup of grape juice has a whopping 38g of carbs (154 calories). You don't even get any Vitamin A or C in that. YOu do get 2% calcium and 3% iron. That's it. I really think you can do better, if you're going to drink something. A cup of Coke has 26g of carbs - so you're getting way more than a sugary soda drink!
On to the raisins. Raisins are just dried up grapes. This means all the water has left - and you are left with concentrated sugar. A cup of raisins has a whopping 98g of carbs, plus 493 calories. You do at least get some iron here - 17% - as well as 8% calcium and 6% Vitamin C. Still ... 98g of carbs! Almost 500 calories! In comparison, a bag of M&M Candies is 240 calories. So you're getting 2 full bags worth of calories in that cup of raisins.
I realize if you're putting a treat in a lunchbox that raisins look great. And certainly, if you're trying to wean someone off of candy, you're sort of moving in the right direction, even though you're actually increasing their sugar intake. I would really recommend you look at other alternatives - apples, berries, anything else that would be appreciated without the sugar.
Lisa Shea's Library of Low Carb Books