Hi LoopyLoo,
I've been in your shoes before.
My take is that the bowel prep will only worsen a flare (but it doesn't happen to everyone I think) and you have to be on treatment once finish your scope, or it could get worse. I was on a mini flare and it became a moderate one post-scope the last time I did one. The bowel prep did worsen it IMO.
The scope is necessary though for the appropriate course of treatment. You might want to check w your doc if meds will be prescribed after the scope or only when you follow up with him/her for the scope results.
Hang in there and best of luck! It's not easy but it might comfort you knowing that you're not alone