I hope you don't mind me butting in (cause we don't know eachother) but you really sound as though you have your heart set on including Ianto in your invitations & it has reminded me of an invitation my mum has had on her fridge for a few years now....
It is basically worded as though the angel baby was inviting everyone itms? off the top of my head it says something along the lines of "Please come along & help me celibrate my mummy & baby sister who I watch over every day." It also askes everyone to bring a plate of food & small candle to light to "help my presence be felt on the day"

Have a wonderful day at your baby shower! No matter the wording of your invites, or the activities you chose to partake in, Ianto will be remembered by all on this special day & everyother day. xx