I'm going to try to over-simplify this for sake of logic. What you ultimately decide is up to you.
There are two actions you can take: come out before or after receiving the money.
There are two responses: acceptance or rejection.
By combining these two actions and two responses, you can get four results:
1. Come out before receiving the money and they accept. Best possible reaction.
2. Come out before receiving money and they reject. Essentially everything returns to how it was before the olive branch was offered.
3. Come out after receiving the money and they accept. This response is bittersweet. Although you would still have the financial assistance, there is potential for hurt feelings and a breech of trust.
4. Come out after receiving the money and they reject. You get the money but will likely have even worse issues with your family for not coming out.
You can control your action, but you cannot control their reaction. Assuming it is a 50/50 chance they will accept or reject, you are buying a metaphorical lotto ticket by choosing whether to come out before or after.
The first ticket, coming out before they help out financially, has the outcomes of money and acceptance, or returning to the status quo.
The second ticket, coming out after they help you financially, has the outcomes of you get the money and your family's acceptance with potential hurt feelings or you get the money but potentially lose your family.
Only you can decide how much each of those outcomes are worth to you. If I were making the decision, I would come out before, because to me, the worst possible scenario of no change is better than the bad feelings created by waiting to come out. However, I know that not everyone is in the same situation, so the guaranteed money from waiting to come out might outweigh the risk of hurt feelings from an estranged family.
The entirety of the above post assumes you have no idea what your family's reaction will be. If you have any idea at all if they will accept or not, you can shift the chances away from 50/50 and more into your favor. If you think they will accept, come out before. If you think they will reject, come out after.
I wish you the best of luck with this difficult decision and hope my ramblings have helped make your decision easier.