You have a bit of a quandry on your hands. You need either:
1)More time
2)Less instruments
3)Give up something
4)Spread it out
I think you answered your own question without even knowing it. You can't get more time, so that's out. You said you want to master both instruments, which is a huge order to fill. My humble opinion says keep life simple and learn one. Mastering is probably impossible, guys like Frampton, Clapton, Satriani and Beck most likely will say they haven't mastered the guitar. Dave's been playing for some 40 years,and he still practices. I think he would agree it hasn't been mastered. There's always something to learn. But there's light at the end of the tunnel. You could play both instruments well, but having taken on that task will require double the practice. Since you are new to the mandolin, i would practice that one at my best time of the day (in your case, morning) Save the guitar (or piano)for the evening. Actually, i'd sell the piano, and re-coup your investment on the mandolin. Maybe buy another guitar, or some cool effects pedal for that tiger Les Paul.