Two days without.
It's quite possible you wouldn't need express during that time anyway.
Express pass is very much worth it when crowds are high or very high. We found it easy to tour without it for moderate crowds - but knowing which rides had longer lines beforehand was helpful. With low crowds, it wasn't needed and we didn't have to worry about certain rides even. (Though, now that Kong is open, that probably isn't the case!)
As for fitting it all in 2 days, don't forget that there's more than just rides. If you are a single person or an adult couple, then it will be a lot easier to fill in what you want than if you're a family.