Well going back to your introduction you already mentioned setting up your own bank account.
Usually after the bombshell news is broken, the advice is to take time out before rushing to make major decisions, who moves out of the family home, relocation, new job, buying a new car. you will have prepared for this for a long time, H may not have a clue and be completely unprepared. In fairness you will have to allow him time to catch up.
Without walking round the house attaching post-it notes to material things, how do you foresee splitting things up? Do you each run a car at the moment? Won't you resent H starting or continuing an expensive hobby or pastime?
Is there anything practically speaking your DH can do but you can't because if you are able to pay someone to do it, that's fine but will you be able to afford to do so?
I would think that you will need to be prepared to face your DCs and explain why for you, divorce is a positive step, whilst at the same time appreciating they may not rejoice with you. Be prepared if you initiate a split for your H to become the 'victim'.
Do you envisage staying on good terms with in-laws, do you have supportive family?
Socially do you have your own friends, are you used to going out by yourself, have you been on holiday alone since meeting H and since having children?