an interesting situation-please help

I will start the presessional program next week with short-term student visa. After completing program on 11st September, I will start my Master program on 14th September.

I am planning to bring my dependents. However they cannot come to UK without having a Tier 4 visa. Unfortunately, I will have a Tier 4 visa, just after 11th September (completing pressesional course)

I would like to be with my family as soon as possible. What should I do? My solutions;

1- Finish presessional program, take new CAS number, apply Tier-4 visa with VIP option and then my family apply Tier-4 visa from my country.

2- Before finishing presessional program, arrange a business invitation for my wife and child (I am not sure it is possible for a child but I have prominent contacts who can give invitations easily)

3- Other solutions ?

On the other hand, I have a financial support letter from my government. Is using this letter seperately with my dependents acceptable? Does it decrease the probability of getting visa ?

Thank you for your helps.

option 1 is better, cost effective, less hassle