You never know, someone may be reading this to research their own overland journey, so I'll try to remember to log GPS info of useful places hereon. I think everything up to now is logged elsewhere on the HUBB.
Sudan

I've lost the GPS to this first one, so some simple directions. Camping near the Nuri pyramids. Camping not permitted at the pyramids (so we were told by local police).
So return down the tarmac road (the 'Dam Road') and take the right turn towards Merowe. (Still tarmac). After a few km, on the outskirts of a village there's a large expanse of open land on the right, sandy and covered with bushes and paths, extensively used by locals on foot and donkeys. Beyond are large palm plantations.
Go onto the land and find a space amongst the bushes for a tent. Someone will approach, ask if it's OK to camp.
Two approached us, both said OK, one returned later with tea for us.
Many locals stopped by in the morning for a chat.
A large 4X4 with us camped within sight of the tarmac road, no problem.

Camping at Meroe pyramids between Atbara and Khartoum. OK to camp here, let the on-site wardens know your intentions. Word is that if you say you're on a tight budget with not much money, you can camp for free.

Bakri's garden. 50 miles from Khartoum on road to Gedaref.
N15deg 9.364' E33deg 6.688'
Go along good dirt driveway towards location, ask anyone you see about camping. If no one around peer through gate or fence, someone will turn up.
Be prepared for late-ish departure next day. (See previous posting).

Halfway between Wad Madani and Gedaref.
N14deg 7.441' E34deg 23.398'
Ridge enclosing a lake on left of road with easy access behind. Out of sight of road if at the right place tucked behind the ridge.

Close to Gallabat and border.
N13deg 3.353' E36deg 2.279'
Dirt track leading to water hole away from road. Likely to be muddy in rainy season but possibly good place for wildlife.

Ethiopia

Between Sudan border and Gonder.
N12deg 37.687' E36deg 39.111'
Dirt track leading to large open area when dry. Likely to be muddy in rainy season and cultivated, with maybe little space to camp. Greet the children when they arrive.