Reading through the replies so far I feel it hasn't been made clear enough that it is indeed perfectly possible to play three or even all four strings on a modern violin at the very same time. Not talking about an arpeggio here.
This works because if you put down the bow on,say, the d-string, apply enough weight and are not too close to the fingerboard, it gets the string low enough that the a and g strings sound as well. If you release the built-up tension very fast, you get a clean chord of three or even four notes simultaneously. Again, this is not an arpeggio, all three strings sound not in very quick succession but at exactly the same time. The same is possible for all four, though not often used. Even though needs to fine-tune the contact point, bowing spreed and pressure fairly precisely to achieve that. (When it comes to holding out triple chords longer, that's where it gets devilishly difficult. It is theoretically possible, but except from nasty exercises to torture poor violin students, I cannot off the hat think of any literature where it's actually required.)
There is a section in Arthur Grumiaux' recording of the g-minor fugue by Bach that illustrates this technique of quadruple-stopping quite astonishingly. (Even though Bach most likely would have simply played an arpeggio.)
Examples where triple-stopping was probably intended by the composers would be near the finish of the exposition of the Bruch violin concerto (g-minor, No 1), or some parts of the first movement of the Brahms D-major one.
I agree that, in this case, it would be perfectly alright to play these notes as an arpeggio. Or the lower two and the upper two in succession, or something like that, mostly a case of personal preference. And I also agree that this chord is a bit out of place in a supposedly easy piece, since it's fingering is a bit inconvenient.
And for a beginner playing this piece it would be far from me to recommend doing anything else.
But, again, just read through the comments and felt it sounded like some kind of arpeggio would be the only way to play this, which is not the case - if that was already abundantly clear I apologize for a well-meant, but entirely useless reply.