Efficiently detecting distance in children objects

is there a way for a parent object to efficiently detect if a target object gets within a certain distance from any of his children objects?

Something like this should be fine, and it's optimised to use square distance values, to avoid the square root involved in computing the distance between two objects.

var threshold : float;
private var thresholdSqr : float;

function Start() {
    // pre calculate square threshold, for use later in optimised distance check
    thresholdSqr = threshold * threshold;
}

function CheckTargetRange() : boolean {
    for (var child : Transform in transform) {
        var distanceSqr = (child.position - transform.position).sqrMagnitude;
        if (distanceSqr < thresholdSqr) {
            return true;
        }
    }
    return false;
}