Ditto what Sugarcane said. Your attention is divided when you are with friends, and you cannot count it as undivided attention.

That is one way to handle it.

Brainstorm. What other options are there? What exactly is your wife uncomfortable about? Would she be more comfortable if the babysitter was in your own home?

How old were your other children when she was comfortable leaving them?

What about a babysitter in your home in one room watching the kids, while you're in another room? It may sound extreme, but that is how you brainstorm. Come up with radical ideas, even ones that may initially sound weird or impossible, and pick out the ones the two of you like. Make brainstorming a fun experience.

Personally, I know a lot of people push babysitting for parents of young children, but it's not really feasible to get all your UA in with babysitting. And it can be very stressful for the mother -- not only leaving your baby, but also having to get the other kids ready to go to the babysitter's house.

UA at home, while the kids are in another room watching a movie, can be just as fulfilling and enjoyable as going out. The kids can soon learn that they are not to bother Mommy and Daddy during your UA time. Perhaps you should save the babysitting for later when she will be more at ease?

Brainstorm together!