Santa suits scared me as a child. I think when I was a child it would have been more helpful if the priest had the little children come up after mass and kneel together before the infant Jesus and adore him. I would have remembered that, especially if kids did it together as a group.
I’m guessing that this wouldn’t work too well. In our Family Mass, the children gather near the front of the nave (not around the altar) for a special homily (it’s appropriate for adults, too).
Many children are simply too shy or apprehensive to do this, and they remain in their seats near their parents. That’s OK, the priest has a mic, so we can all hear his homily.
Last night during Family Mass, the children were invited to come forward for the homily, and although many came, many had their parents come up with them, and many did NOT come, but remained safely in their seats. And quite a few came up, saw the crowd, and ran back to their parents!
So IMO, many shy children would miss out if they were invited to come up and adore a statue of a baby in a manger.
I don’t see any problem with having a saint (NIcholas) make an appearance after the Mass.
Last night, we had the Holy Family come up during the procession at the beginning of the Family Mass (our parish patron is the Holy Family), and the angels and shepherds came with them, and formed a Nativity, which remained at the front throughout the entire Mass. This isn’t in the liturgy, but it certainly seemed appropriate for Christmas Eve. The children who presented this were so incredibly well-behaved and sweet! They also presented the gifts, BTW–very poignant for all! And Father invited all families to come up to the manger after the Mass to see the Holy Family, and everyone who came received a little gift (candy and a nice Christmas card).