If you're already using the Invision app, there's no need for Tapatalk. Don't cater to members who look at necessary change as a bad thing; Those are not the people you want representing your community and you should do what's best overall. You either adapt to change or get left behind. They do not bring growth to your site.
Our board used it for barely a few weeks and then promptly removed it after numerous reoccurring issues, one of them being that it would not honor group permissions consistently and members could access content they were not meant to see, including staff-only content. We were told it was a temporary issue and would be fixed, but then it happened again after the "fix", so we said adios and just dealt with not having an app.
We still deal with not having an app because the Invision app does not work for non-forum communities, but we manage.
ahc's post in Is Tapatalk access a good idea? was marked as the answer