Adding juice to a running ferment

[NormandieStill]

So... started pressing apples this morning. With three of us, we managed to crush and load up around 100kg of apples. The juice is coming off at 1.048 and will be fermented with a champagne yeast to get it as close to dry as possible. The problem is how long it takes to press. We got a pretty good amount of juice off just while loading up the press (About 20L all in) and then by pressing a little got up to around 45L. Since then, I've been ratcheting up the pressure about once every hour or so but I suspect we're now into the realm of diminishing returns. I'm going to keep going until this evening and keep an eye on what comes off to see if it's worth the time and effort.

So all good, except that's about half the apples, and my little "press gang" won't be available until next weekend. Either I drop in some campden and hold out for a week (which for obvious reasons, I really don't want to do), or I start the ferment today on the ~55L of juice, and then top it up next week when we press the rest.

We'll be adding juice to a running ferment which is obviously going to bring some oxygen with it, but given an active fermentation I don't see any obvious risk to the ferment.

I would just split it, but I have one 120L fermenter and no easy way of splitting the ferment out (without tying up a bunch of buckets and a lot of floor space for a few months).

What sayeth the hive mind?