In lockdown it was DS GF birthday, It was at the time people were allowed in gardens only. He cooked her a lovely dinner and strung the Christmas lights all over the tree in the garden and put the table outside underneath the tree. She loved it.
My best birthday recently was walking in the Peak District and when we got to the top of the place we hiked up to DH produced a mini bottle of champagne and a cake.
For fun when DS was little we made his Dad a three course dinner and DS dressed up as a waiter, we drew a fake moustache on him and he wore a bow tie. We made a menu and DS with some help from me was a waiter at the table, he was 6.
We also did quite a few competitions so make assault courses in the garden, have football dribbling competitions, throw balls at stacked up cans. Stuff like that.
You could cover a box in paper and make a lucky dip with little gifts in like a bar of chocolate, make some home made gifts to put in.
One thing we liked doing was having pudding competitions. So ice cream, sprinkles, wafers, fruit, biscuits were put in the middle of the table and people created their own dessert. A certificate of best pudding was given to the best pudding in the eyes of the youngest child at the table.
I had an absolutely joyless awful childhood so in doing small things with my DS and DH I gave DS the childhood I would have liked. Doing little things together is lovely and I hope you have a great birthday with him.