Hi Janey
You are giving the Losec granules correctly.
Domperidone takes 7-9 hours after administration to reduce my half in the blood,
http://www.medsafe.govt.nz/profs/Datasheet/m/motiliumtab.htm and will continue to move food through the stomach for some times so it's timing isn't crucial. Ideally on an empty stomach would be best - so before/with Losec, before feed around 2pm and before feed around bedtime.
We currently give Domperidone with the Losec before breakfast, half an hour before lunch at school and just at the beginning of dinner at home.
Previously Gem needed the Domperidone effect more overnight and less at school so had it before breakfast, at 3pm and then at about 9.30pm before we went to bed. She has had surgery for her reflux since then and things have changed.
Hope that helps.