Integrating an accelerometer to determine altitude will probably not give good results. For years high power rocket altimeters have used a digital pressure sensor for altitude measurement. The Freescale mpx4115a has been a standard device. There are some newer versions that would work too. On the pressure sensor data sheet you will notice a resistor and capacitor on the output of the sensor to microcontroller ADC pin. You need these. Don't leave them out. You'll use the pressure sensor to watch the drop in pressure. When the pressure measured equals the desired altitude pressure pop the chute. You need to Google "Standard Atmosphere" . This will allow you to determine what pressure you'll be looking for. When the altimeter is powered sample and find the voltage equivalent of the AGL pressure. Subtract the voltage equivalent to your desired altitude this will give voltage the microcontroller will activate the deployment at. Here is the Freescale data sheet.
MPX4115A You'll need at least 10 bit resolution. Also you'll need to experiment on the altitude to trigger the deployment to allow for a little coast. Search the rocket forums and NAR about the holes you need to put in the electronics bay. There size and placement is important. You really should go to a high power launch to see someone prep rocket electronics. International Rectifier corporation makes 10 amp logic level FETS that are small and can be driven by the microcontroller directly to power the ejection device. A non pyrotechnic deployment system is hard. I've used a piece of spectra thread wrapped with nichrome wire to hold a compressed spring. Then the FET applies power to the wire it melts the thread releasing the spring. The other easier deployment strategy is to fire you ejection device based strictly on time. Use a pull pin to detect launch and start timing.
Use a long ejection delay on the Aerotech as a backup.
DO NOT underestimate the complexity of the electronics and deployment. Time is running out. Your main focus should be on the physical design of a rocket that reliably flies to that altitude and a parachute for total time. Hint - an overly stable rocket may be a good thing.