No Chimney? Make a "Magic Key."
Tuck a key into a miniature stocking or gift box and leave it outside so Santa can get in at night.
This is a delightful idea sent in by Kay Burgdoff of Hastings, Mich., and it all came about when her young niece moved from Michigan to Colorado. Kay made a small red felt stocking with a white cuff and tiny poinsettia decoration; then she stitched a green and gold loop on the top for hanging it on the front door. Inside she stitched a length of red ribbon that had a house key attached to the other end. That's the Magic Key!
And what is a Magic Key? It a key for Santa so that he can open the front door and have easy access to any houses that do not have a chimney for him to use. Inside Kay put a short poem to explain to Santa just in case he didn't know what it was for, and the stocking was then hung on the front door for him to find on Christmas Eve. What a fun idea and one that should certainly calm the concerns of any 3-year-old who lives in a house without a fireplace.
Kay also mentioned that she got her key at the lumberyard where they make duplicate keys. Just for the asking they were willing to give her any that they had that hadn't turned out just right. I would guess that any place that makes these duplicate keys would also have some available, just in case you don't have any "who knows what this fits?" keys around the house.