Knowing next to nothing about Syriac Orthodoxy but knowing something about Scandinavian Lutheranism and culture, could be something modeled after Lutheran Confirmation as it's a thing around this corner of the World. Among Lutherans, theologically speaking it's not so much of a big deal but in practice it's probably something similar to First Communion in Catholic cultures. Kids being taught basics of their church with additional fun activity organized by their parish, followed by first communion and again followed by celebration with extended family.
Assumingly OO kids get their first communion as an infant but since they're immigrants in Sweden and local majority Christians have this nice traditional Christian feast with extended family, maybe local OO families told their parish "Hey, we want this too"...? I'm a convert with no kids so I have no idea what EO families around here do but our parishes have adopted this custom too in the sense that around the same age as Lutheran kids get confirmed our parishes organize some extra activity to local Orthodox teens.
Here's some Google translated info on this.
