Fahim,
It really doesn't matter what eyepiece you use - both planets are small, especially Neptune. Neptune won't show much of a disk at all.
Last night EP wise I was using a Hyperion Zoom at 8mm, and I had both planets in the FOV. Both close to the edge of the FOV, but still easy to see both together. Tonight they will be even closer. I'll be using as high magnification as seeing will allow. Last night seeing wasn't great, but 340X was usable. If the same conditions are on tonight, excellent!
Alex.
PS, Nick, no offence taken, though it's a bit rich coming from a grown man who plays with train everyday...