Help with first electronics circuit
First of all, welcome to the world of electronics. Thanks for uploading a schematic, as it is much easier to read than a diagram. I have a couple suggestions considering your level.

Use low-side gate drivers

The ESP8266 chip outputs 3.3V logic signals that could not turn any standard MOSFET completely on. That being said, there are many great integrated solutions to address this problem such as low-side gate drivers. One great example is the cheap and easy-to-use TC427. It is characterized for 12V operation and 3.3V logic inputs. Use \$ 1 \mu F \$ and \$ 0.1 \mu F \$ decoupling capacitors near the chip and you've got a simple but effective interface between your SOC and the FETS. You'll need two of them to drive three FETs (2 drivers/chip). As for the FET selection, at such a low current (about 333 mA per FET), it does not make a significant difference, although the IRLB8721 does have lower ON resistance and gate charge, which should generally decrease global power loss.

Use a 5V linear regulator

For the sake of simplicity, start with a 3-terminal linear regulator (7805 type). As Transistor said, it is inefficient but manageable at currents below \$ 100mA \$. Switching regulators are complex and should not be built by beginners. Anyhow, typical current consumption for ESP8266 with 1024 packets at -65dBm (much likely your situation) is 62mA, which should dissipate \$ 0.434 W \$ in the linear regulator. Use a proper heat sink to keep it cool. If you plan to transmit with the ESP8266, power will increase and you will need a proper switching regulator (off-the-shelf, do not build one from scratch at this point).

Stay safe

Double check your connections before applying any power. Have fun with this project.