Your DH has to be completely on board with adoption. Sometimes people go through 'cold feet' patches during the process (that's relatively common and usually resolved) but it's imperative that you both partners start the process with the same desire to adopt.
Usually people have brith children first then adopt. I tried the other way around (didn't succeed in becoming pregant), but I would seriously recommend not to go the same route. If you know you want both, then birth children first.
The other thing is, how strong is your desire to have a child? Realistically, to make it through the adoption process and through parenting an adopted child, you really need to have gone through the process knowing that having children was the most important thing in your life. You shouldn't be thinking "I'd love a child, but I wouldn't be bereft if we never did either. I could be happy either way" because whilst you may have a lovely lifestyle now, adopting will dramatically and permanently change it. People (including me) seriously underestimate how much their whole life will change. And the fact is, many adopted children do have a lot of emotional issues. That may involve going through times which test your marriage to it's limits (that's why it's vital you both have the same desire to adopt. So one partner can't say 'I can't live like this any more, and it's your fault because you talked me into it'). I can honestly say i've been to hell and back with my oldest two, but even in the worst times I felt that I couldn't live without them (even though I couldn't really live with them either!) because my life wasn't a good one without children in it
If your DH wants a baby badly, then you shouldn't adopt, because it could lead to serious problem later. SS will test your commitment to adoption from the get go, and they wouldn't recommend a couple where one partner was much less willing than the other
You might revisit adoption later if your DH one day changes his mind. But adoption is not for everyone, and the desire for a biological baby can be very strong. If it's not for him, then adoption is not right for you either