I have had products that have said next day and taken 3-5 days to delivery , and i complained to amazon and got compensated for the issues
its worth letting them know , as they do need to keep on top of any promises on the site , as they do not want disappointed customers and over promises
as i say , this has happened a couple of times to me and often, when I wanted a tool by the weekend to do some work each time once complaint has been accepted and understood, Amazon have been good in making sure I'm still a happy customer.
you probably need your son who ordered it to complain , especially as he ordered based on the information on the site, that you would be getting it by your birthday
with regard delivery, this is typically amazon, just left on door step, or outside or neighbour - very rarely do they knock or leave a note
But i have never lost anything, and would prefer to find on doorstep then the agro of a redelivery or having to collect from a postoffice sorting or other of the centres they use
I would say 80% of the time, i get the items on the first day mentioned on the delivery or earlier - BUT some do take a while