well,my mom and I have done an Angel Tree for the children that dont have homes,etc.For the kids,we just sent the the essentials,tooth brush,clothes,some toys,a hair brush etc.
Probably for dogs,i would send food,treats,Blankets,some balls,I would definently bring some blankets b/c they always need blankets at shelters.
ive never done an angel tree for doggies yet,but hope that helped a little