Dependants application after main applicant

[2013uk]

Hello All

I hope you will be able to help me with this case

A family of 4 need to renew their stay, main application is on T5 and visa will expired by the end of the month, however his 3 dependents are not able to apply before their visa expiry because the amount require for their maintenance will be short by 20 days, is it possible for the main applicant to send his application before his visa expired (his maintenance is cover by sponsor) and then send his dependent applications 20 days after their visa expire, in order to have the required 90 days maintenance requirements on his account? will they be any problems?

Thank you very much in advance.