Hi Grouse,
I’ve owned multiple Tri-Star’s and still own many different Beretta and Benelli auto’s in both 20 and 12g. I owned a viper G2 20g which shares the same mech to the one you’re talking about and a close friend owns the exact one your talking about.
The Tri-star for your use case here will work perfect. It’s soft shooting and I found them to be quite reliable. I will say I broke different pieces of the bolt on my 20g G2 (extractor one time and the locking bar inside the bolt another). Both of those were after thousands of 7/8 trap load rounds and both times it was pheasant hunting w/ 3″ 1 1/4″ heavy loads. Both times Tri-Star sent me replacement parts fast, no questions asked, and for free (I believe they were out of Kansas).
If you go into the purchase understanding you’re not purchasing a Benelli or Beretta auto, you’ll be very happy. No it doesn’t have a cole trigger like you may see in a high end Beretta or the pure reliability of a Benelli – but the price reflects that. TBH, I’ve got a Rem 1100 with a youth stock I put together for my nephew and the overall weight of that gun was an issue (even with a 24″ barrel) – the Tri Star seems to be preferred by most the kids we’ve shot around.
My son is 8 and when he’s a little bit older that’s the gun he’ll be starting with. Feel free to PM me with any specific questions.
Pete