Birthday gift and celebrations for my boyfriend
You could orchestrate a romantic gifts hunt around town having your boyfriend find clues that lead him from one surprise to another and at the end he will find a larger gift or surprise. To create a romantic gifts hunt around town you could leave the first clue inside his favorite coffee cup leading him to his favorite store where a gift certificate will be waiting for him along with another clue. Continue this hunt leading him from one place to another, places you know he will enjoy, leaving him to find small gifts (such as birthday balloons, chocolate kisses, love tokens etc) and more clues.
Eventually, you could lead him back home to the mailbox where a love letter from you will be waiting and one last clue that will send him to a romantic spot of the two of you to spend a nice evening together.