A think out the box solution, if your mom's health is a concern, and you don't "need" the baby gear, is to wait after the baby is born, and have a "meet the baby party." You can have men and women and children. It can be informal, you can even have a backyard breakfast with lots of quiche, ham and cheese croissants, coffee, donuts, and bloody marys and mimosas. then guests in small groups, 2 or three at a time see, hold, coo at the baby, and get a photo with him/her.
If you are planning to register, be smart about it, with 100 guests to contend with, register for items 0-18 months, so you can have a bit of everything to see you through the first year and then some, rather than 100 newborn outfits your baby will quickly outgrow.
Good luck to you and yours.
F. B.