Have guests write down their wishes for the baby-to-be. I guarantee that the mom-to-be will cry when she reads them and saves them all in the baby book to read again some day.
I suggest handing these out as the guests arrive as it will give them something to do while waiting for the other guests to attend. The mom-to-be can read out them loud, but I suggest just having the hostess gather them to give to the mom-to-be to read later.
You can design and print up your own Wishes for Baby cards or order pre-printed Wishes for Baby cards pretty cheap from Amazon.