This is a great question because a lot of us have been there. The first thing you can do is make sure to take the batteries out of your toys before you ever leave home. If your toy is rechargeable and doesn't have batteries that you can remove, then check for a safety switch. It's like airplane mode for a sex toy. This will save you a lot of trouble and embarrassment. You certainly don't need any extra guards coming over to pay you a visit. A lot of people who travel with their sex toys pack their sex toys in their carry-on bag because they don't want to risk the toys being stolen or lost.
If, for some reason, your bag is searched, then the best you can really do is just roll with it. Most people who work in the travel industry won't give you too much of a hard time unless there is some sort of language barrier between you. Most of the TSA agents in America will find it funny Don't be embarrassed if you get caught. Everyone who travels with sex toys eventually gets caught. It's like a traveling sex toy rite of passage.
Oh, and awesome job trying to surprise your wife!