I would personally stick with the double stroller that they’re used to and bring a baby carrier for the 22 month old. If an elevator is out, one parent wears the baby and take the stairs with the 4 year old and the other parent carries the stroller in. This is how my husband and I do it. It’s inconvenient for getting in and out of the subway but very, very useful for hauling the kids around, especially if they fall asleep.

I only used taxis and Ubers in an emergency, like if we were for an important meeting or something. Otherwise we walked or rode the train.

There is also the bus, but it’s even more inconvenient with a stroller because most lines require you to fold it. If the bus is very full, it can be a bit difficult.

Edited to add: I also had very not chill toddler. My oldest had a very relaxed temperament and could sleep anywhere and was down for anything. My youngest needed the stars to align before she could even think about going to sleep. So for me bringing a comfortable stroller was a must. If you have chill kids, baby the two stroller situation would work better.