neru mae ni, kodomo ni mouhu wo kakete agemasu.

Because 前 is a noun, and when a verb comes before a noun in Japanese, it usually appears in its plain form, not the ます-form.

So:

• 寝る前 = before sleeping / before going to bed
• not 寝ます前

This is the same pattern as:

• 食べる前 = before eating
• 行く前 = before going
• 勉強する前 = before studying

So 寝る前に is the natural grammar pattern.

前 means before, but as a noun it often needs に when used as a time expression.

So:

• 寝る前に = before sleeping
• literally, at the time before sleeping

The に marks the time point when the action happens.

In this sentence, it shows that the action 子供に毛布をかけてあげます happens before going to bed.

In this sentence, 子供に marks the person who receives the action.

The verb かける here means to place/put something over someone, as in putting a blanket over a child. So the child is the target of that action.

• 子供に = on/for the child
• 毛布を = the blanket

You can think of it as:

• put the blanket (を)
• onto/for the child (に)

Also, because the sentence includes あげます, the child is clearly the person receiving the favor.

Because 毛布 is the direct object of かける.

Here, かける means to place or drape something over someone. The thing being placed is 毛布.

So:

• 毛布をかける = to put a blanket on someone / to cover someone with a blanket

The blanket is the thing directly acted upon, so it takes を.

かける is a very broad verb in Japanese and has many meanings depending on context.

Common meanings include:

• to hang
• to put on
• to wear certain items
• to make a phone call
• to pour
• to apply
• to cover someone with something

In this sentence, 毛布をかける means:

• to put a blanket over someone
• to cover someone with a blanket

This is a very common use with things like:

• 毛布をかける = put a blanket over someone
• 布団をかける = put a futon/blanket over someone

〜てあげます means to do something for someone.

So:

• 毛布をかけます = I put a blanket on the child
• 毛布をかけてあげます = I put a blanket on the child for them / as a kind act

The あげます adds the nuance that the action is done as a favor or kindness toward someone else.

In this sentence, it suggests the speaker sees this as a caring action for the child.

〜てあげます often implies:

• I did something for someone
• the action benefits that person
• there is a sense of kindness, help, or favor

But it can sometimes sound a little self-aware or slightly patronizing if used carelessly, especially with equals or superiors, because it can imply I generously did this for them.

With a child, though, it is very natural, because caring for a child is a normal context for 〜てあげる / 〜てあげます.

So here it sounds warm and natural.

Japanese often leaves that ambiguous unless the context makes it clear.

So 寝る前に could mean:

• before I go to bed
• before the child goes to bed
• before we go to bed

In real life, context would usually decide.

Because the sentence is about putting a blanket on a child, many learners may assume it means before the child goes to bed, but it could also mean before I go to bed, I put a blanket on the child.

Japanese often allows this kind of subject ambiguity.

Both are common.

• 子供
• 子ども

Many modern materials prefer 子ども, partly because the second kanji 供 can have historical nuance that some people avoid in this word. But 子供 is still very widely used and understood.

So for learners:

• both are normal
• 子ども is often preferred in textbooks, schools, and formal writing today

Yes, Japanese word order is fairly flexible as long as the particles stay correct.

For example, these are all possible:

• 寝る前に、子供に毛布をかけてあげます。
• 寝る前に、毛布を子供にかけてあげます。

Both are grammatical.

The basic roles stay clear because of the particles:

• 子供に = target/receiver
• 毛布を = direct object

That said, some word orders sound more natural than others depending on emphasis and rhythm. The original sentence sounds very natural.

The て-form connects かける to あげます.

This is a standard grammar pattern:

• verb in て-form + あげる

So:

• かける → かけて
• かけてあげます = do the action of putting on a blanket for someone

The て-form does not mean past tense here. It is just the connecting form needed to attach あげます.

Yes. A casual version would be:

• 寝る前に、子供に毛布をかけてあげる。

The difference is:

• あげます = polite
• あげる = casual/plain

You could also hear casual speech with omitted elements if the context is obvious, but the full casual sentence above is a straightforward equivalent.

Both are grammatical, but the nuance is different.

• 子供に毛布をかけます
  = I put a blanket on the child.

• 子供に毛布をかけてあげます
  = I put a blanket on the child for the child’s benefit.

The second one sounds more caring and emphasizes that the action is done as a kindness or favor.

So if the meaning shown to the learner includes a warm, caring feeling, 〜てあげます is an important part of that.