Speech marks and capital letters

[snice]

Can you tell me which of these sentences is correct please:-

"Help me wash the dishes," said Mum, "then you can go out to play."

"Help me wash the dishes," said Mum, "Then you can go out to play."

punctuation inside speech marks, is how I've always been taught.

Capital letters for the second part only if it's a complete sentence and the first sentence ended with a full stop.

'Then you can go out to play' is fine as a complete sentence.

'Help me wash the dishes, then you can go out to play' is not a complete sentence without a conjunction, although I accept that in informal language, it would be fine.

So my view would be NEITHER is right.

I'd have punctuated/changed it in one of these ways:

"Help me wash the dishes," said Mum, "and then you can go out to play."

OR

"Help me wash the dishes," said Mum. "Then you can go out to play."