Need help with an Airsoft Prop

Hello I need help building a circuit for an prop bomb. This will in no way be used to detonate any substance and is a toy/prop. What I want the circuit to have is as follows: First you run to a place and you open the suitcase and inside is a button. The bomb planter must hold down a button for about 10 seconds and the bomb becomes armed with 4 7-segment LED displays turning on and begin counting down from 5 minutes after that 5 minutes if the bomb is not disarmed a buzzer goes off and the 4 LED displays letter that spell BOOM etc. I would also love for the circuit to have a disarm button that if held down for 20-30 seconds would turn off the circuit rendering it safe and the game is called. Thanks for all your help and again this will not be used for any real explosives and is only a prop for airsoft games.

Seems to me that this project is best solved by using a microcontroller.

Obtaining the discrete ICs for this project would be problematic, and would allow little flexibility.

Get yourself a PIC flash starter kit they don't cost a lot of money. Once you get your head round simple programming, input / output and delays you will find that you never need to look for any other bit of kit.

One of these PIC's will do everything you ask and lots more.