These days, baby showers don't have to be held at a home at all. In fact, what was considered unacceptable just a few decades ago is now the norm. While it wasn't the one thing to celebrate private moments in a restaurant, now it's even a logical or practical thing to do.
What's changed is the way that we live. Homes are now shrinking and there isn't really that much space to squeeze in more than six or so guests, much less all your friends. Plus, these rules were made when it was more common to have hired help in the house or at least a cook or a housekeeper. Now that everyone has to do their own work, it's much easier to just have a baby shower at a restaurant instead.
Of course, any restaurant could do, even a McDonald's if you’re trying to evoke at atmosphere of becoming a kid again. You could even ask them to host a kiddie party for you complete with games, prizes, and a cake plus a kiddie meal.
Ask your guests to come dressed as a kid and to be prepared to act as one as well. Think “13 Going On 30” for this party. All you'll need to do is change the music soundtrack to what was popular when you were a child, whether it was 80's music or hits of the 90's. Just that simple addition could make you a child again.
McDonald's or any fast food place which offers birthday party packages for children would be perfect for baby showers like these since they already have a private room prepared, food packages, cake, prizes, and even entertainment and decorations thrown in. All you need to do is show up.
If you'd like a more staid restaurant instead, check the amenities. What's most important to a mommy-to-be is having a lavatory nearby and possibly a rather private area to rest for a bit.
Reserve a private room if you can. This will at least contain the party and also allow the guests to act as silly as they like. You won't have to worry about disturbing the other patrons if you laugh too loud or make a lot of noise.
Decorations shouldn't be obtrusive or hard to cart in and out. Little paper decorations like silly party hats and personalized place cards may be enough. Ask permission about stringing a few curls of metallic streamers across the table. Don't use paper, it might stain the cloth if it gets wet.
If there is no private room, you could ask for a private table in a far corner of the restaurant so you disturb as few of the diners as possible. That would mean keeping the noise down, though, and restricting games to the more sedate ones.
Lastly, the bill. If you are footing it, your guests would understand
if you give them a budget that would fit in an adequate meal and
a drink. Or, you could confer with the chef and pre-order a meal
for everybody. Don't ask people to pay for their own food, though.
That's considered really impolite.