Do not overspend. It is always possible to do something special with your grandchildren. It may be fun for them to help you make a cake or cupcakes for their birthday. Give them your undivided attention and spend quality time with them - children always enjoy that. You can create a collage from the pictures you have of them. Write a nice card sharing memories with them that are special to you. You shouldn't just focus on the gift. You should think about the thought that has gone into the gift.