Currently we are sending our Campaign Data on the first page... that said, I am not sure if that is the best.. but so far in our implementation we are still trying to figure out how to get context variables added to our lifecycle metrics. While it should be possible, our developers broke lifecycle when they tried (we're using React Native), and we haven't had a lot of time to investigate this much, so it got put on hold.
Part of my concern over what is the "right" solution, is that on web, the Instance of Campaigns is available to correlate to the actual page view.. whereas on mobile app, it's either on the page view (but not the first hit of the visit) or it's on the first hit (lifecycle) but then the campaign is only the attributed data and not the instance. So there's lots of considerations...
I wish I could merge the lifecycle metrics into the first page and get the best of both worlds.