I know at least one school that allocates DTA for PE Teachers activites outside of school and according to the STPCD 2011 any activities as specified by the Head teacher must count toward DTA and additional payments are available for this if not within the DTA.
If I were your Wife, I would get hold of her Union Rep and ask to see the latest STCPD so that she can see whether she is entitled to extra payments for running such activities or whether they are part of her DTA.
I will ask her later, perhaps some extra income she didnt realise she was entitled to.