It is absolutely OK to register for the gifts if you are doing it in the reasonably priced store and you keep to small things like onesies, blankets, diapers and cosmetics. This means that your guests are about to have some much needed guidance about choosing the gift. Keep it small and simple and it will work out for the best for everybody. I always suggest registering for a variety of items including larger items like strollers, car seats, ect. There are some people who want to splurge on the larger gift items or sometimes people will pool money together to get a bigger item.
Usually, if the party is of the smaller scale and you are having the home based get together, a nice playlist for your PC will be all the entertainment you need. For a rented place, you may want to change this and hire some live performer who will make the party memorable and interesting. A guy with a guitar will be just enough for a party of 30 to 50 people.
Food and Drinks
For home based option, you should make sure that you prepare some light snacks, at least. The best idea is to coordinate between people who are coming to the party and ask them to prepare something and bring it. For hired venues, you can do the same, or you can simply solve this by hiring a caterer as well. You should take care of the drinks. Once more, depending on the crowd, you should get more or less alcohol. But, even if the whole party is completely booze free, nobody would refuse a glass of dessert wine just to make a toast.
Usually, the baby shower is thrown for the first born baby. However, nowadays, it is quite common for people to have showers for second and third child as well. In the end, it is all about good will and getting together to celebrate and give support.