I'm sure many of us have had similar experiences with delayed bags. However yours (96 hours, 2 infants, international destination) gets my sympathies.

That aside, my most recent experience was a domestic transcon where my bag did not show up for 48 hours. For that, I was reimbursed for a change of clothes, basic toiletries and supplies (total about $100) as well as received a goodwill travel cert. I would expect at least the same for you.

(Tip, I would keep any potential ranting to a minimum when I communicate with United. It doesn't seem to help.)