Zucchini are very easy to grow. I am thinkin' you should figure about a 2'X 2' square for each plant. Maybe larger if you don't want 'em runnin' into each other. And you'll get *lots* of squash from 3 plants.
I also think you will find that your basil will satisfy even your impatience! It germinates easily and grows *fast.* :-) It's one of those things (along with radishes) that is kinda fun to let kids plant because things happen fast with it, and it is prolific.
I am still disgusted with my lack of ability to get sage to grow here. I mean, this is Texas. Sage is supposed to grow wild and overrun the countryside! Never had a problem with it at any other place I lived. And other people here in town don't have problems. There is something *wrong* with my yard!
I THINK I'd have enough room for that. And starting from seeds would be fine for zucchini, I'd think.
I'm still considering 'maters...but nervous about the whole staking deal. Dunno if I'd get that right.
As for sage...I cheated on that and bought plants, and I'm still hoping they flourish. They're still alive after a week of being outside in the ground...but don't look altogether happy yet. I'm keeping my fingers crossed!