Mechanics Question

[Chess Ref]

Doing a 12 U tourney game today.

I"m BU. Player hits shot down RF line , I hook inside and as batter runner is going around 1B the F3 backs into her. The pretty typical "I'm 12 and don't know what I'm doing move.". The BR gets splathered and I give the DDB signal and verbalize OBS. BR gets up and goes back to 1B. RF nows throws the ball into 2B....AT this point I call "Dead BAll" . I announce the BR is awarded 2B. And we go on.

Partner believes I should have waited to announce award till after ball is in the pitching circle. His thinking was the F4 could have throw the ball away and the player may have been able to advance to 3b etc. At the time I killed the play nothing was going on but does he have a point ?
I tried, a little anyway, to find something in the book about waiting till play was over but couldn't find anything...

What say you ?