I'm in the same situation as you however, I think I have the most precosious foal in the history of foaldom!!
What I did in preperation for weaning was put mare and foal into a herd so that foalio had friends already. However, foal has now decided her friends are way cooler than mum and mum has decided that her friends are less hassel than foal so apart from the odd occassion when foal wants a drink they are seperate. I am going to seperate them out into seperate fields in a couple of months but if either one finds it too stressful, I have the contigency plan of a field far, far away for mum.