I am not involved at all in his day to day business activities.
When he was setting things up, we talked about how to make things work, how to set things up, business bank accounts, how he would "pay" himself, etc.
We do talk about new clients, how much work it will mean and whether or not to accept a new client. That does impact me/our family and is not necessarily just a business decision. I think you and your DH should talk about this. When a new business is starting, it can mean a shift in how things work around the house, who does what, evening/weekend work, etc. This will be complicated in your case by the fact that he has a partner and cannot just make those decisions on his own.
Beth, mom to older DD (8/01) and younger DD (10/06) and always missing Leah (4/22 - 5/1/05)