You are planning two parties and inviting people to both
One is a baby's party: ninety minutes of attention, a nap that must not be missed, cake arriving at a moment you have chosen deliberately. The other is a grown-ups' party, where people want to know whether they are eating, whether they are staying for all of it, and where the buggy goes. If the invitation answers only one of the two, the other half of the room spends the afternoon uncomfortable.
Say what the day actually looks like, in order, and the tone of the whole thing changes. Parents stop asking questions in the group chat because the answers are already in front of them.