How do I disinvite someone?

I planned a small birthday gathering and asked n a group of good friends if they want to come, but what I didn’t saw is that there was someone who I‘ve known a day and they were the only person out of the group who told they would come. I don‘t know them very much and they don‘t fit into the group of people who will come to my birthday. Its planned for in two weeks and they write me constantly how happy they are that I invited them, but I don‘t really want them to come, but I don’t want to disinvite, because they seem nice, but just not in my inner friend circle yet. What do I do?