Honestly, if you show up gives the star fighter squadrons something to defend. So sooner might be better than later I am also curious to what kind of forces the Imperials are bring to the fight, space wise.
We can make a separate thread for 'big ships' to duke it out, if the Imps have anyone to command them.
To be honest, I hadn't envisioned Rebel Star Destroyers. If you're going to show up with one then a) keep it limited (the Empire's forces should far outnumber the Rebels) and b) wait a bit, so it acts as reinforcements.
Keep in mind that the Rebel fleet will have been largely battered during the Skywalker mission. I envision most of it having landed and being in serious disrepair. That's why they're hiding on Naboo, instead of just going back to their bases.
Don't think of this as fleet vs fleet. Think of it more as a much smaller version of the Rebel fighter squadrons vs the Death Star. A small scale vs a much larger scale. Which is fine, because none of you can die unless you want to, so the potential to create something epic is ripe.