お母さん、牛乳買って来るから、お風呂洗ってくれない


> お母さんが男の子に頼んでいます。
>
> お母さん：ねえ。
>
> 男の子 ：なあに。
>
> **お母さん：お母さん、牛乳買って来るから、お風呂洗ってくれない。**
>
> 男の子 ：ええー。もうすぐ見たいテレビが始まるんだけど。
>
> **お母さん：牛乳、買って来るのと、どっちがいい。**
>
> 男の子 ：ええー．．．．．．お菓子も買っていい。
>
> お母さん：一つだけよ。
>
> 男の子 ：わーい。じゃ、行って来る。わ、あと１０分だ。自転車で行こう。

I don't understand how to translate the sentences marked in bold.

In the first one, why would mother use the word お母さん in here own speech? Is
she asking him to go and buy milk and then to wash the bathroom or is she
asking her son to wash the bathroom after she comes back from buying milk?

In the second one, I don't understand the usage of どっちがいい. We have one one
option here (which is buying milk), so why would we use どっちがいい?




> お母さん、牛乳買って来るから、お風呂洗ってくれない。  
>  I'll go buy some milk, so (while I'm out shopping) can you wash the bath?

As for this usage of お母さん referring to herself, see: [When referring to
herself, is there any pronoun other than お母さん when speaking to her
children?](https://japanese.stackexchange.com/q/25947/5010)

This does not mean "after I come back" (that would have been 買って来てから).

> 牛乳、買って来るのと、どっちがいい。  
>  Which do you like, [washing the bath] or go buying the milk?

The other option (washing the bath) is simply omitted because it can be
inferred from the context.




> お母さん、牛乳買って来るから、お風呂洗ってくれない。  
>  I'll go buy some milk, so (while I'm out shopping) can you wash the bath?

As for this usage of お母さん referring to herself, see: [When referring to
herself, is there any pronoun other than お母さん when speaking to her
children?](https://japanese.stackexchange.com/q/25947/5010)

This does not mean "after I come back" (that would have been 買って来てから).

> 牛乳、買って来るのと、どっちがいい。  
>  Which do you like, [washing the bath] or go buying the milk?

The other option (washing the bath) is simply omitted because it can be
inferred from the context.

