travel to zaventem airport

Hi,

I am searching to find ways to travel to zaventem airport from stockel, WSP by bus/train this Saturday. I found there's a STIB bus no. 21 running from Schuman to Zaventem (meaning I will take metro (Stockel -> Schuman)then bus). Does anyone know how long it takes for the bus trip? The web says the bus runs all stops on Sat.

It only takes 10-15 min. by car from my house to the airport. Should I just save the hassle and reserve a taxi? (btw, which taxi is the cheapest?) I paid 38 euros one-way from airport to home last year. Is it what I should expect for this year as well?

Is there any other cheap yet feasible way that anyone recommends to travel to the airport for two adults with a little kid and a big luggage?

Thanks in advance for your prompt attention.