[ryuurui]

I am jolly sleepy but I think it should be リーさんは土曜日にたいていテニスしてますか？, though it will have a slightly different meaning. (Lee, on sat. you do mostly tenins?)

you could use いつも instead of たいてい as it would sound better in this case.

リーさんはいつもの土曜日にテニスやってますか？

But wait for our forum's native speakers to confirm this.