If the keg has been below 40F this whole time, your original plan should work great. Leaving it at 10 PSI for an hour won't be any different than leaving it there for 2 minutes, just to serve your test. If your test seems properly carbed, just leave it at 10 PSI. Otherwise, bump it back up to 30 and check it every 4-5 hours. If you leave it at 30 until Sunday, it will likely be over carbed. I would target letting it sit at 10 for at least a day before service, to let the carbonation stabilize.
I've done the shaking thing, and while a bit risky towards overcarbonating, it does "work". I have a hard time recommending it though, because if you're not very careful you will get beer in your gas line and possibly your regulator, and it's easy to overcarb.
One more note, you didn't ask about this but, be aware that if this is a brew that you're hoping will serve clear and you didn't clarify with gelatin BEFORE kegging it, it's pretty likely that transporting the keg is going to kick up the sediment in the keg and the beer won't serve as clear as you were expecting. When I have to move kegs like this for anything I want to serve clear, I clarify with gelatin in keg1 and, a day before the transport, I do a closed keg transfer to keg2. If that's something you're interested in, I can tell you my process.