Hi all - sorry if this has been asked before but have a question about using 2 241s.

We are a family of four in a household account. I have 1 241 (expiry feb 2020) and expect my next one in about 6 weeks. I want to book all 4 of us onto A flight (availability not an issue at the moment). Do I have to wait until the 2nd voucher to do this or can i do 1 for 2 of us now and the other 2 when the new voucher arrives. My thinking is the first but though I'd seek calification