asita no ryokou no tame ni, konya no uti ni nidukuri wo owarasemasu.

It means for tomorrow’s trip or in preparation for tomorrow’s trip.

Breakdown:

• 明日 = tomorrow
• の = links nouns, like ’s or of
• 旅行 = trip
• のために = for the sake of, for, in preparation for

So 明日の旅行 is tomorrow’s trip, and 明日の旅行のために means for tomorrow’s trip.

Each の is connecting one noun to another.

• 明日 の 旅行 = tomorrow’s trip
• 今夜 の うち = literally the inside/extent of tonight, which becomes by sometime tonight / while it is still tonight

In Japanese, の is very common for noun-to-noun connection. It does not always mean exactly the same thing in English, but it often works like of, ’s, or a general modifier.

Here, ために means for, for the sake of, or in preparation for.

In this sentence, it gives the purpose of the action:

• 明日の旅行のために = for tomorrow’s trip
• then the main action is packing and finishing it tonight

So the idea is: I’ll finish packing tonight for tomorrow’s trip.

今夜のうちに means while it is still tonight or before tonight is over.

This expression has a special nuance:

• うちに often means within, during, or before the time/state changes
• 今夜のうちに strongly suggests get it done sometime tonight, not later

So it is more specific than just saying tonight. It emphasizes the deadline: before tonight ends.

That is why 今夜に would not express the same natural meaning here.

うちに marks a time range or limited period during which something happens.

In this sentence:

• 今夜のうちに = before tonight is over

This pattern often appears when the speaker wants to finish something before a certain time passes.

Examples:

• 今日のうちにやります。 = I’ll do it by the end of today.
• 若いうちに勉強する。 = Study while you’re young.

So here it gives the feeling of I want this completed within tonight’s time window.

They are part of set grammar patterns:

• ために = for / for the sake of / in order to
• うちに = during / while / before ... is over

So this is not just a random extra に. These are standard expressions you learn as chunks.

荷造り means packing or packing luggage.

It comes from:

• 荷 = baggage, load
• 造り = making/preparing

In natural English, you would usually translate it simply as packing.

So:

• 荷造りをする = to pack
• 荷造りを終わらせます = to finish packing

Because the speaker wants to say not just I’ll pack, but I’ll finish packing.

Compare:

• 荷造りします = I’ll pack / I’ll do my packing
• 荷造りを終わらせます = I’ll finish packing

The second one focuses on completion. It tells you the packing will be fully done by tonight.

終わらせます means finish something or bring something to an end.

Important difference:

• 終わる = something ends / is over
• 終わらせる = to end something / finish something

So:

• 旅行が終わります = The trip ends.
• 仕事を終わらせます = I finish the work.

In your sentence, 荷造り is the thing being completed, so 終わらせます is the right choice.

Normally, no. That sounds unnatural because 終わる is intransitive, so it does not normally take a direct object with を.

Use one of these instead:

• 荷造りが終わります = the packing will finish / be finished
• 荷造りを終えます = I will finish the packing
• 荷造りを終わらせます = I will finish the packing

Your sentence uses 終わらせます, which clearly shows the speaker is actively making sure the packing gets finished.

In Japanese, the non-past form covers both present and future.

So 終わらせます can mean:

• I finish it in the appropriate context, or
• I will finish it

Because the sentence includes time words like 明日 and 今夜, it is clearly understood as future.

The subject is omitted, which is very common in Japanese.

From context, it is most naturally understood as I:

• I’ll finish packing tonight for tomorrow’s trip.

Japanese often leaves out subjects when they are obvious from context.

The basic structure is:

• 明日の旅行のために = for tomorrow’s trip
• 今夜のうちに = by tonight / before tonight is over
• 荷造りを = packing
• 終わらせます = will finish

So Japanese is placing:

1. purpose
2. time
3. object
4. verb

That is very typical, because the verb usually comes at the end.

They are similar, but there is a nuance difference.

• 終えます = finish
• 終わらせます = finish something, often with a slight sense of making sure it gets done

In many contexts both can work:

• 荷造りを終えます
• 荷造りを終わらせます

But 終わらせます can feel a bit more active or deliberate, as if the speaker is determined to complete it.

They are very close, and both relate to tonight.

A simple way to think about it:

• 今夜 is a little more formal or written-sounding
• 今晩 is very common in conversation

In this sentence, 今夜のうちに sounds very natural.
You may also hear 今晩のうちに, but 今夜のうちに is a very common set phrase.