syuumatu ni tomodati to issyo ni hanabi wo mi ni iku node, ima kara wakuwakusite imasu.

No, each に is doing a different job here.

• 週末に = at/on the weekend
  This に marks a time.

• 一緒に = together
  Here, に turns 一緒 into an adverb-like expression, so it describes how you go.

• 見に行く = go to see
  This に is used in the pattern verb stem + に + 行く / 来る, which shows purpose.

So although they all look the same, their functions are different:

• time marker
• adverbial marker
• purpose marker

友達と一緒に means together with a friend / with friends.

• 友達と = with a friend / with friends
• 一緒に = together

Using both makes the idea more explicit: not just with a friend, but going together with a friend.

Compare:

• 友達と行く = go with a friend
• 友達と一緒に行く = go together with a friend

Very often, 一緒に adds a feeling of doing something side by side.

Because in the pattern verb stem + に + 行く, Japanese uses the verb stem, not the dictionary form.

• 見る → stem: 見
• 行く = to go

So:

• 花火を見に行く = go to see fireworks

This pattern is very common:

• 食べに行く = go to eat
• 買いに行く = go to buy
• 会いに行く = go to meet

So 見るに行く is not correct in standard Japanese.

This is a very common structure:

object + を + verb stem + に + 行く

It means go in order to do something.

In this sentence:

• 花火 = fireworks
• を = marks the thing being watched
• 見 = stem of 見る (to see/watch)
• に = marks purpose
• 行く = go

So the whole chunk means:

go to watch fireworks

It is not two separate actions like watch and then go. It means the purpose of going is to watch fireworks.

ので means something like because, since, or as. It gives a reason.

So:

• 花火を見に行くので = because/since I’m going to go watch fireworks

Then the result comes after it:

• 今からわくわくしています = I’m already excited now

So the sentence structure is basically:

Because I’m going to go watch fireworks this weekend, I’m excited already now.

Compared with から, ので often sounds a little softer, calmer, or more explanatory.

Because before ので, Japanese normally uses the plain form.

So:

• 行くので = correct
• 行きますので = also possible in polite/formal speech, but less basic and more formal/business-like

In everyday learning, it is best to think:

• plain form + ので

Examples:

• 忙しいので = because I’m busy
• 雨なので = because it’s raining / because it is rain-related weather
• 行くので = because I’m going

In this sentence, the speaker still ends politely with います, even though 行く is plain. That mix is completely normal.

Here 今から means from now / already at this point.

So 今からわくわくしています means:

• I’m excited already
• I’m excited from now, even though it’s still before the weekend

It emphasizes that the excitement has started before the event.

A few rough nuances:

• 今 = now
• 今から = starting now / already from this point

In this sentence, 今から gives the feeling of I can’t wait.

わくわく is an onomatopoeic or mimetic word that expresses excitement, anticipation, or a thrilled feeling.

To turn it into a verb-like expression, Japanese often uses:

• わくわくする = to get excited / to feel excited

Then:

• わくわくしている = be excited / be in an excited state
• わくわくしています = polite form of that

So in this sentence, わくわくしています means the speaker is currently in a state of excitement.

This is similar to many expressions like:

• どきどきする = feel nervous / heart pounding
• いらいらする = feel irritated

Because わくわくしています focuses on the current ongoing state.

• わくわくします can mean I get excited or it is exciting
• わくわくしています means I am excited right now

Since the sentence also has 今から and talks about present feelings before the weekend, わくわくしています fits very naturally.

It gives the sense: I’m already feeling excited now.

Sometimes time expressions can appear without に, but with 週末, 週末に is very natural and common.

• 週末に友達と一緒に… = very standard
• 週末友達と一緒に… = possible in casual contexts, but less clear and less standard for learners

As a learner, it is safest to use 週末に.

In general:

• some time words often do not need に: 今日, 明日, 毎日
• others often do use に: 週末に, 土曜日に, 三時に

Japanese nouns usually do not change form for singular vs. plural.

So 花火 can mean:

• a firework
• fireworks

In this sentence, the natural English meaning is fireworks, because people commonly go see fireworks as an event or display.

So even though the Japanese word itself does not show plural, the context tells you the intended meaning.

Because the main predicate at the end is a verb phrase:

• わくわくしている → polite: わくわくしています

You use です with nouns and adjectives in certain structures, but here the sentence ends with the verb する in its -te iru form.

So:

• 元気です = I am well
• わくわくしています = I am excited

Both are polite, but they use different grammar because one is built with です and the other with a verb expression.