当面 and ひとまず: a policy for the present and an initial action
Compare maintaining the current method for now with making an initial reservation, checking which follow-up action remains.
A policy for the present and near future
当面, read とうめん, means for the present or for the time being. 当面はこの方法を続けます。 says that this method will be maintained for now.
当面は予定を変えません。 says that the schedule will not be changed for the present. It does not establish a permanent refusal to make any future change.
Taking an action as a first step
ひとまず means for now or as a first step. ひとまず席に座ってください。 asks the person to sit down first.
ひとまず予約しましたが、後で人数を確認します。 says that a reservation was made for now, but the number of people will be checked later. The two actions have different timings.
Read the follow-up plan and conditions too
ひとまずここで終わりにしましょう。 suggests ending here for now. Further context is needed to determine whether or when the activity will continue.
ひとまず does not grant free cancellation of a reservation. Describing an initial action and stating the actual reservation conditions are separate matters.
Has the number of people already been checked in ひとまず予約しましたが、後で人数を確認します。?
Show the answer and why
No. The reservation was made, but the number of people will be checked later. Keep the completed action distinct from the follow-up action.