Appropriate food for young blackbirds

Two pairs of blackbirds come to my back door for food and I have been offering raisins, which I cut up into two or three pieces in case they may be too big for the young, and have been soaking for an hour or so, especially in this very dry weather to give a little moisture to adults and young alike. The adults choose these with apparent delight but am I doing the right thing. They come back every 15 minutes or so but I only give a few each day as I presume the young need a great variety of food.