I'm so following this thread. Had something similar in my fleet a while back.
For what it's worth....the Telemini is THE avionics package for something like this. AFAIK, nothing else on the market comes close to providing deployment and tracking needed for something like this (taking into account available space and mass allowance). And yes, it is RF only, which is plenty good enough....while it is true that GPS has become much more the norm these days it seems, there is a long history of rocket tracking via RF before GPS was so affordable and available to the masses. Get some advice from folks with experience in RF tracking - it will serve you well.
Can't wait for more, and hopefully some successful flight reports,
good luck,
s6