I’m going to be in Hong Kong 7 days what should I use for MTR card?

I don’t arrive till 4pm so thought I’d just purchase a round trip airport ticket. Airport to TST. (It’s my understanding that the return can be used anytime within 30 days). Then use unlimited “Airport Express Travel Pass” with pass to validate beginning day 2 of my stay, because I plan to go to Expo in middle of my stay. Can I go to airport on my first airport express travel pass trip ticket then use the 2nd Airport Express travel pass to return from airport to begin its use unlimited for next three days? Also can I purchase airport to expo ticket round trip same day return? Is all this worth it to me to not deal with octopus reloading cards?