I'm looking to raise money from angel investors and would be focused on the startup 110%.
I do, however, have some prior commitments that I had made for some short term consulting.
I will easily be able to handle both at the same time (and the consulting commitment is only for 3 weeks).
You really shouldn't do that after raising money.
Investors are putting their money on the line for you to grow your business -- so they can get a return in the future. It's a big responsibility (for you) to live up to.
The client you formed the previous commitment with would understand if you were to break it. Do mention why you would not be following up on their consulting commitment: because you raised money and have a bigger responsibility to the people who have already put their money on the line.