If you are buying express like you say, you should be fine either way.
I'd personally recommend doing the tents first as later in the night, those lines tend to get shorter while the IPs stay long all/most of the night. Also, one of the Parade Building queues (which isn't being used this year, but maybe the route/path will for a new Sprung) is always a disaster for express. Not sure why, but they always just make Express stand there forever at the merge point. The sooner the better with that house. So if you do them first, you have the option of hitting them up again at the end of the night with a sub-30min standby queue as the long queue / originals "back there" get small wait times later in the night so that would be fun to spread out the runs a bit. Also, there have been rumblings that the Uni Monsters house might have a "different winners/endings" type thing. Haven't seen any insiders say that, so it might just be wild guesses, but that has been a trend lately at the event and the house seems to lend itself to that kind of ending, so having some leeway built into your plan/schedule to try to do it twice spread out could be a good idea.
Also, keep an eye on the forecast as the tents sometimes flood and they close them...often times for extended periods of time. Maybe that's gotten better as the last couple years my group has miraculously missed crazy rains and I know they put in raised walkways, but just in case there are later storms in the forecast, ensuring you get them done earlier would be a good idea. And the new tents are a total question mark, so after the event starts, I'd keep an eye out for any issues/closures with the new tents.