if you are principal applicant then your points will main important to qualify (like age , language points your work experience etc ), your spouse points you can claim only educational points or any relatives like mother, aunty/uncle brother sister (if she graduate or master or PHD holder) it will count to claim adaptability points.
your wife and son also migrate with you as dependants.
you can land with them but they can not land before you becasue you are the PA. they can also land after your landing but before expiry of visa or medical or passport.
you need POF (proof of funds) for 3 (near about CAD $18500 to show enough POF with application to CIO , even Visa office ask several times updated POF, finally you also want that when you get visa and plan for land in Canada once you land at Canadian airport the POE officer will ask to your POF).
you have to read this and start preperation:
http://www.cic.gc.ca/english/pdf/kits/guides/eg7.pdfread manual before apply you will get many answer from this manual if you have any query in mind.
OMM