TAMP eligibility is determined by your SPD (Sep Program Designator) code on your sep orders. The Airman and Fam Readiness Ctr can translate. Have MPF get this right the first time vs amendments.
Quick story: The week before I was supposed to start terminal, my kid was hospitalized all the way through my guard transition and then some. I know you're concern, mine's worth well over $1M at 10 months old-- I've read "The Book" on TRICARE. DEERS was a headache. 30 days is the window for retroactive enrollment, and it almost took me that long to get DEERS unscrewed. TRS was a good interim option for my family until I got the TAMP thing sorted out (a whole other story)... And once you figure that out, plan on falling off the face of the earth again (as far as DEERS and TRICARE are concerned) once you get back on orders in your ANG unit. Title 10 orders will turn off your TAMP (family included), if that's a factor for you. Good luck-