My experience has been that people who raise these issues are genuinely afraid of their ability to parent an adopted child. This isn't a reason not to adopt, but I would advise that you think long and hard about what you both want.
My husband was initially against adopting our first child. He was adamant that he wanted a bio child first and that we would adopt second. Two weeks after we got home with Jonah he looked at me while he held his sleeping child and said "what was I thinking, not wanting to adopt????"
To help understand your husband's hesitation, I would suggest you go to some free classes sponsored by agencies in your area. He might feel free to express his concerns in that forum. (When we went, my normally reserved husband was full of tough questions for the SW and it was quite an eye-opener.)
As for keeping the adoption a secret, two things: the child will likely not look much like you. It's going to be a safe bet to assume that people will know on sight, and thus your child will eventually see the difference in himself and you. Honesty is really the best policy about adoption, and your husband may just not be ready.
On the issue of bonding, our son came home at 7.5-months of age and there have been no bonding problems at all. We belong to him, and he to us. And to us, it's no different than if we have given birth to him.
Kelley