Tier 4 dependant visa /established presence

Hello everyone , I would be grateful for any advice given on this situation . I have studied in undergraduate recently and had to go home no later than 5 months to apply for my for my master degree visa which I currently have. I would like to apply dependent visas for my children. as my parents who takes care of them are travelling for a longer period . However their father is present in the UK but I have sole responsibility on them (a single parent ) . My question is that the maintenance money requirement as an established student (which i think I am ) Do i need to show ''only'' 920 pounds to be in the account for 2 months or do i have to include my own maintenance for two months as well . Secondly ,would i need to get a letter from their dad as well to show his consent bearing in my I have the sole responsibility. would be grateful if anybody can explain how to write a covering letter to back this up .

Your replies will be much appreciated

Anyone plsssss i need your contribution to this issue of mine . it is really confusing . pls help !!!!!!!