Interference or no call

[tornado]

Pony league baseball. Runner on first. Batter doubles to left and tries for third. SS accidentally runs into him and knocks him down about 1/3 of the way from 2nd. Batter/runner scrambles back to second, just beating the throw from left. Runner from first had stopped at third while the interference(?) took place. Without the interference I would probably have had two runners on 3rd.

Ruling please? No harm, no foul, leave the runners at 2nd and 3rd, or should R3 get home and batter/runner get 3rd?

Thanks in advance...