Interference?

[rwest]

Rule 8-7-P says

When, after being declared out or after scoring, a runner INTENTIONALLY interferes with a defensive player's opportunity to make a play on another runner.

I was calling a game up at my church and had the following happen. Now this was a minor league baseball game with young kids. I guess probably in the 4th/5th grades. I know its baseball and this is a softball forum, but I do mainly slow pitch softball and was wondering how this play would be called in softball.

R1 advancing from third on a base hit. He scores. The defense had thrown home to get him out, but overthrew the catcher. The ball went to the back stop. The catcher recovered the ball. R2 is also advancing home. Here's were the problem occurred. R1 is still standing on the plate, forcing the catcher to either go around R1 or through him. Would you consider this interference? I really don't believe it was intentional and by rule it has to be in order to call interference. The kids are still learning the game at this age. So what would you call?

I put R2 back on third base without an out and allowed R1's run to score.