We make the reindeer food each year - A bit of bran so the reindeer can sniff their way if it is foggy and a sprinkle of glitter so they can find their way in the moonlight. DH has the job of sprinkling it just before DS goes to bed on Christmas Eve. The first time we used this it was truly magical. It began to snow as DH was sprinkling the stuff and all the glitter shone in the patio lights. Next day DS looked out and, in the snow were some fox tracks which DS was convinced were reindeer footprints and, of course, right by their side were the boot prints from DH the night before which DS was sure were from Father Christmas boots!
We also have a magic, glittered cardboard key which we put outside on Christmas eve. We have a fire place but it's a log burner and DS was worried the big man would get stuck so we used a key DS made at nursery. Great it you have kids worried about people getting in the house as the key can't open any doors, only Father Christmas can make it work.
We started, last year, to have an advent calendar with little books for each day. The books tell the Christmas story. So we decorate the tree with the books, DS finds the right one each day and we read about Mary and Joseph, King Herod or whatever and then he puts the book in the calendar. I am hoping that'll be something he can keep going each year. We used to do the ordinary advents but they just tore so easily when DS was smaller - he is six now.
And our final tradition is that I have squirreled away one of DS's old bell musical rattles. As soon as we hear him stir on Christmas morning I dash out of bed and shake the blessed thing outside his room! Then I dash back to bed. Every year he comes rushing in to us shouting that he's heard the bells, Father Christmas has been! Magical!
Oh, and of course, we leave the mince pie and carrots out for the reindeer and either DH or I will cut off the top of the carrot and bite it so there are reindeer teeth marks in it!
Just be careful that you don't do as my sister used to. She got into the habit of doing a present for Father Christmas which they left with the mince pie etc. Which was fine until my niece started noticing that Father Christmas's slippers or whatever were remarkably like her dad or grandad's so my sister started to buy from a charity shop, hide it and give it back after Christmas - waaayyy to complicated!