Hello

I'm trying to book LHR-Japan (either airport) fir a family of 4 using an Amex 241 voucher. Getting availability on the voucher is fine as I'm booking a year in advance, but what is really tricky is booking a reasonable fare for the extra two seats. It seems I cannot book one way tickets like I can with avios, so my choice seems to be book my 241 and then wait for the whole return leg to be available to book- is that right or is there a workaround? At the moment it is more expensive to buy one extra economy fare than two club seats on the voucher. It's a busy time of year so fares seem to increase very quickly (May/June 2020).

Any help appreciated!

Thanks