I am so envious,You will have so much fun whether you go trick or treating with your granddaughter or have fun at home. Kids are so fun when they are little. They get so excited about everything. I remember years ago, when I took my 3 year old nephew trick or treating, when people would open their door , he would say trick or treat then want to walk into their homes and make himself comfortable, eat some candy, watch tv, hang out with their pets, etc. He was ready to change his home address and move in with the families at every house we visited. After we explained that you don’t go into the homes, you wait outside the door and say trick or treat, he would get his candy and then sit down on the porch or steps to the home to immediately eat his candy. He became very tired after trick or treating at 8 or 9 houses, so we took him home and he watched movies. He refused to take off his costume before going to bed, so we let him sleep in the costume ( not the mask / face covering) and he went to bed bed exhausted, happy, and slightly sticky from eating candy.
Have a wonderful trip!