Do 13 things for good causes...
Set his alarm 13 minutes earlier next week, each day
Try 13 new foods (fish/salmon, new crisp flavour, snails, squid, tofu, venison, pease pudding, curry, celeariac, etc...)
Give 13 thoughtful comments to 13 people over the next 13 days
Take 13 personal items (socks, gloves, scarf etc...) to a homeless shelter
Ask him for his 13 best things in life to date
Read 13 pages of a book a week
Take 13 food items to above
Learn to say hello my name is .... in 13 different languages
Delete 13 people off social media that are there just because...
Write a 13 line poem or song
Give £13 of his birthday money to a good cause/charity