Yes buying something from the BA Shopping portal would work.

Not sure where you are based but if in the UK and your husband has a Nectar Card with more than 400 Nectar Points then link it to BAEC and do a transfer of 400NP which will give him 250Avios

Also not sure what BAEC status you or your husband have. If either of you have Bronze or higher then that will protect all Household account members and no one's Avios will expire