Guide to Yokohama during weekend

Hey, my family is planning to go around Yokohama before heading to Narita.

Do you think all the places will be packed at the weekend?

We plan to go to the ramen museum, the aquarium, and Chinatown as a day trip.

When you say "aquarium", do you mean the Sea Paradise? If so, yes, Ramen Museum, Sea Paradise and Chinatown are always crowded during weekends, and since they're far apart from each other, it's not very practical to do them all in one day.

Why not see one famous establishment and stroll around to see the city instead of the spots? For example, you can dine at Chinatown, and walk to Yamashita Park and all along the harbor. The area also has smaller museums like the Japanese Overseas Migration Museum and/or the Silk Museum where there would be less people, as well as old brick establishments like the Port Opening Memorial Hall where you can look inside.

https://www.jica.go.jp/domestic/jomm/index.html
https://www.silkcenter-kbkk.jp/museum/
https://www.kaikokinenkaikan.com/facility/
https://www.yokohamajapan.com/

You will board minato mirai line
From yokohama, you will go motomachi chuk agai station,then 5 min walk to yamashitacho

The train (or bus) you take depends on where you're coming from. For example, there are a couple of JR stations that are close to Chinatown, while you can also start your walk from further stations. And, of course, you can focus on the newer side of Yokohama such as Sea Paradise and Ramen Museum if those are the areas that interests you more.

Certainly, these three places are far apart.
Sea Paradise may take about half a day to see.
You can save time just by making it a cup noodle museum instead of a Ramen Museum.
However, depending on the time of your visit, you may not be able to experience the factory.
If you want to visit three places, the Ramen Museum starts at eleven, so you may want to do it last. Some shops in Chinatown are open from the morning.
https://www.chinatown.or.jp/tag/breakfast/

If you are looking for something to fill out your itinerary, the Yokohama port Osanbashi hall building is a pretty cool building that you can walk around/ on top of for free. It is between Chinatown and the Cup Noodle museum.

Ramen Museum - you pay to get into a crowded building, queue for ages to then pay for a small bowl of over-priced noodles and then repeat until you are full (possible two bowls). Much better to go to a proper ramen shop or ramen food court where you can chose a decent ramen to your liking. It's hardly a "museum". At least the pot-noodle museum covers the history of that product.

Well, actually, I like the Ramen Museum and sometimes take people there, because it's a cheap way to immerse in a fake 1960s-Japan atmosphere. But the last time I was there, they had started using noisy post-millennium amplifiers for their street performers. I hope it has returned or will return to the place where salarymen of the area bothered to pay the small entrance fee just to enjoy regular beer and old-fashioned pub snacks. Anyway, it's not a place worth visiting unless you have other things to do in the neighborhood.

It will better if you buy yokohama bus pass= 600 yen or minato mirai line 1 day = 460 yen

Yes, more crowded on a weekend. But if you want to eat in Chinatown, eating in mid-afternoon is not as bad as lunch or dinnertime. Walking through is fun also, you can see places like the Yokohama Kuan Ti Miao Shrine and the Mazu Miao.
For me, much better than the ramen 'museum' is the gorgeous Sankeien Garden, which is one of the finest in the region.
https://youtu.be/rmEcl4_fZZs

If you have time and the weather is good, the view from the Landmark Tower is also excellent around sunset.

I would also recommend Sankeien Garden, but it's far from any place else (you need to transfer to a bus to get there), it takes half a day to see everything there, and it doesn't necessarily represent Yokohama as a whole. Since you seem to have little time, I truly recommend walking around in a small area if you want to see what Yokohama is like.

​Instead of Ramen Museum, have a look at Cup noodle museum:
https://www.cupnoodles-museum.jp/en/yokohama/