Bear in mind that you probably wont get away until mid afternoon on monday and will have to return the boat by first thing friday morning.
Check river levels. If the river is up, you only choice is to go North.
If the river is down, the Droitwich Ring option would be pretty good IMO. You get river, narrow canal, wide canal, a big town, a city...
I'd head down the Severn and aim for the floating pontoon at Hawford for your first night, unless you get away in good time and get head down towards Worcester. The Camp House pub is a good choice for a first night too, moor on the end of the lower lock landing with the lock-keeper's permission. Or you could carry on down into Worcester and moor on the river pontoon just past Diglis Locks.
On Tuesday, head up the Canal and aim for Hanbury Junction, but be prepared to moor around Dunhampstead depending on how you're doing for time.
Wednesday, head down to Droitwich and moor on the visitor pontoons in the town basin, or in the park. Or if you fancy a nice quiet mooring there are some nice spots further down, e.g. by Salwarpe.
Thursday, back down to the Severn, upstream to Stourport and moor on the river pontoon just before the locks.
A nice trip.