ame no hi ha zitensya de tuugakusuru kawari ni, haha ni eki made okutte moraimasu.

雨の日 means a rainy day or more literally a day of rain.

• 雨は would mean as for rain, which changes the topic and does not mean on rainy days.
• 雨の時 means when it rains or at the time of rain, which is possible in some contexts, but 雨の日 is the more natural everyday way to say on rainy days.

So 雨の日は sets up the topic as for rainy days...

The は marks 雨の日 as the topic of the sentence.

So the structure is:

• 雨の日は = as for rainy days
• the rest of the sentence explains what happens on those days

This is very common in Japanese when talking about what one does under certain conditions:

• 休みの日は家にいます。 = On days off, I stay home.
• 忙しい時は外食します。 = When I’m busy, I eat out.

Because many time expressions in Japanese do not need に.

Words like these often appear without に:

• 今日
• 明日
• 毎日
• 雨の日
• 休みの日

So:

• 雨の日は is natural
• 雨の日には is also possible, but it adds a little emphasis or contrast

In this sentence, plain 雨の日は is the most natural choice.

Here, で marks the means/method used to do something.

So:

• 自転車で通学する = to commute to school by bicycle

This is the same で used in:

• バスで行く = go by bus
• 電車で帰る = return by train
• 箸で食べる = eat with chopsticks

So で here means by using or by means of.

通学する means to commute to school or to go to school regularly.

It is more specific than 学校に行く:

• 学校に行く = go to school
• 通学する = commute to school as part of one’s usual routine

So in this sentence, 自転車で通学する gives the idea of a normal commuting method, which fits well with instead of.

かわりに means instead of or in place of.

In this sentence:

• 自転車で通学するかわりに
• = instead of commuting to school by bicycle

The idea is that one action is replaced by another:

• usual action: go to school by bicycle
• replacement action on rainy days: have mother take me to the station

A useful pattern is:

• dictionary form + かわりに = instead of doing X
• noun + のかわりに = instead of X

Examples:

• 車で行くかわりに、電車で行く。
• コーヒーのかわりにお茶を飲む。

Because かわりに normally attaches to the plain form of a verb, not the て-form.

So:

• 通学するかわりに = correct
• 通学してかわりに = not natural here

This is just how the grammar pattern works:

• 行くかわりに
• 食べるかわりに
• 勉強するかわりに

You use the plain form before かわりに.

This is because the sentence uses ～てもらう, which expresses receiving the favor of someone doing something for you.

Pattern:

• person に + て-form + もらう
• = receive the favor of having that person do something

So:

• 母に送ってもらいます
• = I have my mother take me / I get my mother to take me

Here, 母に marks the person who does the action for the speaker.

If you used 母が, the structure would be different and would not fit もらう in the same way.

It is close to that, but it has an extra nuance.

送ってもらいます means:

• I have my mother take me
• my mother takes me for me
• I receive the favor of being taken

So it is not just a neutral statement about what the mother does. It is phrased from the speaker’s point of view as something the speaker benefits from.

Compare:

• 母が駅まで送ります。 = My mother takes me to the station.
  
  • focuses more on what the mother does
• 母に駅まで送ってもらいます。 = I have my mother take me to the station.
  
  • focuses more on the benefit to me

Because まで means up to, as far as, or until a point.

So:

• 駅まで送ってもらいます
• = I have her take me as far as the station

This implies the station is the endpoint of the ride.

If you said 駅に送ってもらいます, it could sound less natural here. 送る often pairs very naturally with まで when talking about taking someone to a destination.

Not in the English mail/send sense.

送る has several meanings, including:

• send
• see someone off
• escort
• take someone somewhere

In this sentence, it means something like:

• take someone to a place
• drive someone to a place
• drop someone off

So 駅まで送ってもらいます means the mother takes the speaker to the station.

Because the sentence only says that on rainy days, instead of biking to school, the speaker gets taken to the station.

This suggests a likely situation:

• normally: commute to school by bicycle
• on rainy days: mother takes the speaker to the station
• after that: the speaker probably continues by train or some other method

Japanese often leaves obvious details unstated if the context makes them clear.

Yes. かわりに can also mean something like in exchange for or as compensation for, depending on context.

For example:

• 手伝ってくれたかわりに、夕飯をごちそうした。
• = In return for helping me, I treated them to dinner.

But in your sentence, the meaning is clearly instead of:

• 自転車で通学するかわりに
• = instead of commuting by bicycle

Because it is in polite style:

• もらいます
• instead of plain もらう

The whole sentence is written in standard polite Japanese. That is very common in textbooks and neutral conversation.

A plain-style version would be:

• 雨の日は自転車で通学するかわりに、母に駅まで送ってもらう。

Same basic meaning, different level of politeness.

Here are the main readings:

• 雨 = あめ
• 日 = ひ in 雨の日 → あめのひ
• 自転車 = じてんしゃ
• 通学する = つうがくする
• 母 = はは
• 駅 = えき
• 送って = おくって
• もらいます = もらいます

So the full sentence is read:

あめ の ひ は じてんしゃ で つうがくする かわり に、はは に えき まで おくって もらいます。

Yes. As very often in Japanese, the subject is omitted.

The sentence does not explicitly say I, but that is understood from context.

So the natural interpretation is:

• On rainy days, instead of commuting to school by bicycle, I have my mother take me to the station.

Japanese leaves out things like I, she, or we when they are already clear.