Oops - we have just sold our city apartment for similar reasons. DD is now 2y 9m and needs more space and some outside garden area. We also needed a better school too for when she is older. And if and when baby #2 decided to come along, we need that extra room.
We love our city apartment living. It is modern and lovely. Everything is on hand and so close.
But we had to be practical.
So we have sold up. The sale should go through in a week or two, all being well.
We are buying a new build 3 story town house, with a garden. Still has amenities within a 10 minute walk, but not the same type of thing as we have here. It won't be ready till December though, so moving to a rental property in mean time - think we found the one tonight infact.
TBH, I think you would find your current place too small with another baby in there, and you may start to feel on top of each other. I know I would, for all it's benefits right now.
Good luck with your decision. I know how hard it is!