I can tell you with my bipolar .I dont make any plans at all I cant follow though I hate having to go some where or do something it gets in my head .Life is much much liveable with my head empty.
My other two friends were the same way .We all just lived minute to minute its so much more fun .But then again we all were bipolar .

Try not telling your freind your plans ahead of time just bring them at the time or put little hints into your friends head so they think they thought of it. Thrust me it will work just like everyone (bipolars)we have pattrens we dont think like you so once you learn them you can changes to how you wont .