Thought I was done with kids

I have 2 beautiful girls, 17 and 8. I got married last year to my best friend who I have known for 20 years. We are 42 and 45. He REALLY wants to have a baby. He loves my girls, but they are not “his” pet say. We tried for 6 months (which I know isn’t a long time...but I got pregnant with my girls on the first try one month off birth control). We have agreed to try again. So now what? :/. Should we both be on fertility vitamins? Any other tricks or tips? Thanks ladies.