Please help, which route to take? Marrying on a B2 Visa

[Hopeful2017]

I'm currently in Brazil and would like to go back to the US to live. I have a son here who I've already gotten a US passport for. I'd also like for his father to come with us to the US to live. The fastest way for us to get there and stay there together would be for him to enter the US using his B2 visa then marry after. I'm just really worried that the IO might deny based on dual intent since he already have a son together..... Any advice? CR1 from here is averaging a year.... It's too long.

Any info appreciated. Thanks in advance.