Sweet area for a 'Tank Course'..... Might I suggest that the Job Number 1.... ' Keep the dog off '... is slightly more relevant to 'NUMBER 2's... rather than to number 1's though....
...a few 'logs' might be nice but
not if they come via the dog.....

.
.
Remove the grass... or cut it back to keep it very short.... possibly a contact weed killer where the roads are going to go... ( Once the dog cannot get in ) ...
You want roads, dips and a couple of hills and you
have to have a bridge... with 'railings' so that tanks cannot accidentally fall or climb over the side and risk getting damaged !!
.
Tunnel... constructed from a length of plastic pipe... buried underneath one of the 'Hills'.. don't make it too long so that a 'stuck' tank can be rescued and that it doesn't attract nesting hedgehogs or rodents.
( possible short length or rail way track curving from the tunnel and straight off the tank course... for a 'Kelly Heroes' style appearance !!
.
Sections of wooden fencing.... like lolly pop sticks.. split down their length & glued together... This way they CAN be driven over and flattened but not destroyed.. and so can be recycled by being stuck back in the ground !
.
Buildings... or a couple of wrecks....that can be moved around.... possibly just walls that have a couple of spikes sticking out the bottom to hold them upright.. but still allow them to be flattened by a tank..
.
The potential is truly
enormous....

Never Forget......
The Propaganda of the Victors....... becomes the History of the Vanquished