when you are choosing an embark location from the world you have to pick a rectangular playing area which defines the accessible map, you cannot see beyond this edge but things will come in from it.
The default size I think is 4x4 (the numbers refer to the number of map tiles which make up the embark) but this can be reduced to 2x2 or increased to whatever your computer can handle, the site could even be reduced to 1x1 with mods before but i don't know if that still works.
A 2x2 embark will give you ~96 tiles each way, the size and proportions of the tiles will depend on the tile-set you use, the default windowed tile-set has each tile at 8 by 12 pixels, but you can get smaller larger and squarer tile-sets if you so choose
Tile size/proportions don't really matter because when it's read in text, the map is read as a grid, even if it's taller than it is wide visually, since it's still, for example, 96 by 96. In any case, he'll be running it in text mode, and tilesets won't apply. Minimum embark size is 2 by 2, although with the Nano-Fortress tool you can do 1 by 1. The default is 4 by 4, and anything much larger will lag very early on. Technically the maximum size is 16 by 16, but DF will crash at that size usually.
You could maybe reduce the size of the window. That way, you 'see' less tiles at once, and it might be easier to visualize the map. In fact, if it's small enough, you might be able to avoid being confused by the horizontal reset because you could memorize what items are where. If it's 5 by 5, for example, you only need to keep track of a maximum of 25 tiles. Only some coordinates will be of interest, of course, so the number will probably be much lower with the exception of things like large-scale battles, in which case you can pause and go frame-by-frame. Maybe the grid size function in init.txt would do something... although I don't know if it affects the text-only version.
EDIT: I just tried the text-only version on Linux and attempted to resize the window-- no luck, it segfaults. The grid can't be set smaller than the default 80 by 25 either. By the way, the default window is 23 by 23 squares for the main screen and map, and the menu is 34 squares across, if that info helps you at all.
EDIT2: Does anyone know if you could customize DF with a graphics set or something so the Unicode tiles are something else? The creatures would be fairly simple with some raw-modding, but the terrain would be impossible I think. The languages can be find-and-replace'd for the accented characters.