I took my daughter out for an expensive Saturday lunch to celebrate getting into her top choice. (Okay, I used a gift card I got for Christmas, but it still counts. 
)
We combined the college choice and birthday celebration into a dinner at a really fancy local restaurant. Expensive but a great memory!
I invited our carpool people and son’s best friends and their families over for pizza. He applied in junior year, so no one else had been thru the application process that year.
Son’s grandparents had died the year before, so it was nice to be with a a group of people who knew son well.