Step 1: Analyzing the problem.
The centres of the circles lie on the given circle \( x^2 + y^2 = 25 \). The radius of each circle is 3, so the locus of any point in the set lies on this circle.
Step 2: Conclusion.
The locus of the points is \( x^2 + y^2 = 25 \), corresponding to option (1).