state law determines whether each of you can use the DBA designation or must use the name of the LLC.
while there are no federal income taxes for an LLC or partnership, some states do impose a state income tax. again the laws vary by state. you have provided no info of what the LLC does, how it does it, or even if some of your business may be conducted out of state. So while your resident state may not tax the activities, your business might be taxable in other states depending on their laws.
the best thing you could do is to consult with a professional in your state. there may be major items that are being overlooked. for example do you need to collect sales tax?
