
Cosco Kids
Scenera Next DLX Convertible Car Seat
Super light, cheap, great for air travel, but outgrown fast.

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Not who you asked, but we really like the cosco one. It’s cheap ish so not too pricy as an additional seat, and it’s one of the lightest you the market for carrying through the airport. You can also buy a car seat backpack from 3rd party sellers which was really good for the airport of it all.
I uber all the time with my toddler and we use the Cosco Onlook car seat and use a harness to sit it on our travel stroller. It has worked extremely well and its lightweight and easy to install in cars. My toddler just rides in the tethered car seat when we get out of the uber.
Uh no way am I skipping the carseat. We have the lightweight Cosco one and even when traveling by myself with the I haul it, our luggage and my 3 year old. I usually just rent a car wherever we're going and deal with installing it.
We also do the lightweight Cosco seat with a padded carrying backpack that we check. Set it up so the harness height is situated in advance and make sure you know how to safely install it. Depending on your budget and child’s size (under 45 inches and 50 lbs so likely for a 4 year old but it’s expensive to not be able to use a lot) there’s also the WayB Pico which is super light and compact for travel. i would definitely do a stroller for a 4 year old at Disneyland but would rent there through BabyQuip or at the park. I’d also gently encourage you to learn how to install all of your car seats. Kids can accidentally unbuckle them climbing in and you need to understand the install. Most manufacturers usually have videos on YouTube you can look up!
I'm a parent of 4 and we fly a lot - I'd absolutely bring the car seat on the plane. It's safer, and it gives her a comfortable familiar space to rest. We own a lightweight cosco carseat just for the purpose of travel. Also, there is no limit for amount of breast milk allowed. I'd buy a soft sided cooler that fits the carry-on size requirements and put the milk in there with ice packs. You can also bring a diaper bag for free with most airlines (in addition to your personal bag).
Just grab some lightweight Cosco seats. Much easier to haul through airports. Like 8 lbs each. Then you have them forever and don’t have to worry about a rental screw up If they’re 4 just check the seats with luggage. Grab a basic nylon bag for each.
yeah, you gotta bring your own. same with taxis or even the one time we sprung for black car service with a car seat installed. dude rolls up sans car seat and just shrugs. buy a cosco because it's light, check it for free in a basic nylon bag and just take away the chance someone else screws this up for you.
Cosco Seats for life once you're past the "click into stroller phase". lighweight, fits in an airplane seat and you can likely go 3 across in most backseats. also they're $50 pop

Cosco Kids
Scenera Next DLX Convertible Car Seat
Super light, cheap, great for air travel, but outgrown fast.

Cosco Kids
Scenera Next Convertible Car Seat
Portable, affordable, quickly outgrown, airplane buckle discomfort.

Joie
Mint Latch
Easy baseless LATCH install, lightweight, but quickly outgrown.

Nuna
PIPA Series
High-end travel, easy baseless install, but very pricey.

WAYB
Pico™ Portable Car Seat
Ultra-light, compact travel, quick install, but expensive and outgrown fast.

Ranked #1
Cosco Kids - Scenera Next DLX Convertible Car Seat

Ranked #1
Cosco Kids - Scenera Next Convertible Car Seat

Ranked #1
Cosco Kids - Scenera Next DLX Convertible Car Seat

Ranked #1
Doona - Doona Series

Ranked #1
Cosco Kids - Scenera Next Convertible Car Seat

Ranked #1
Nuna - PIPA Series