The only think that bothers me its that im at very beginning , every tutorial so far is for UNO , and i will not have much time to search "how this and how that works" so i think UNO is safer.... etc the gsm shield , i dont know if it is working good and easy with the mega as with UNO...
To summarise :
--LCD Serial Enabled 16x2 LCD - White on Black 5V - LCD-09395 - SparkFun Electronics - 1 pin
--Keypad http://www.instructables.com/id/Analog-Keypad-Backpack/ - 1 pin
--GSM shield https://www.sparkfun.com/products/9607 - 2 pins (as they said to me , i dont know for sure)
--2in1 sensor Humidity and Temperature Sensor - DHT20 - SEN-18364 - SparkFun Electronics - 1 pin
--CO2 sensor (still dont know which one) - 1 pin (i think)
--2 fans DC Brushless Fan-- 50x50x10mm - COM-09648 - SparkFun Electronics? - 1 pin , they will start and stop together, no speed control
--4 shift registers Shift Register 8-Bit - SN74HC595 - COM-13699 - SparkFun Electronics? - 3 pins per 2 shifts , sum 6 pins (they will control 30 leds , 15leds/2shifts)
1+1+2+1+1+1+6 = 13 pins !
Finally i will need something to open and close some very light cardboard windows... something that will go from A to B and from B to A , not continuously , only when i will tell it to do so... like cd rom tray ! (maybe a servo?) I think it will have 1 pin... i dont know... so i have 14 pins
Can you "see" something wrong in my thoughts ? UNO seems good to handle them and will have some pins free just in case...
Thanks for the help so far , great community !