How to choose MOSFETS by using the datasheets infos?
Pick any of the SOT23-3 MOSFET rated 350mA or above, from a well known brand. Buy yourself a tape of 100 pieces. I don't think you have to worry about anything else in your application.
Most N-Mosfets, nowadays, have a gate threshold between 1.2 and 3V. P-Mosfet have typically a threshold of -1.2V. Which means the gate of a P-Mosfets must be at the same voltage as the source, practically, to be off.
Mosfets with different, and therefore unusual parameters will be exceptions.
It's fine to use a P-Mosfet for M1, but you can also use a N-Mosfet to power your load by connecting M1 to the low side of the load. Instead of connecting it to 5V, you would connect it to GND (The &quot;negative rail&quot; Chris talked about above). Like this you would use only N-Mosfets. It's also generally more efficient to use N-Mosfets. Unless you have a good reason to use a P-Mosfet of course.
I suppose M2 is a N-Mosfet.
R2 is a little bit weak. I would increase it to 100K.