That sounds like me! I had two boys, then #3 came along (GIRL!) when they were that same age (3.5 and almost 2).
I won't lie - when I look back on those first two years of my daughters life, it was kind of crazy. Take LOTS of photos... it will help you remember it all :)
I bought a sit and stand stroller (used - a local Mamasource/Mamapedia mom saw a question I had about them and offered hers up for $50). I would often push all 3 of them on it, the baby in her carseat clicked in the front, the toddler on the seat and my 3 year old standing. It was the best $50 I spent on baby gear.
Other than that, my advice is sleep when you can. Try not to stress the small stuff. Take help when offered :)_
J.