The simplest way is probably to have Linked Record fields in the Players table for each membership level. Call the fields Junior Membership, Senior Membership and Honorary or Life Membership. Then link the relevant record in each field fore every player in the Players table. You’ll then need to have three Look Up fields (Junior Membership Fee, Senior Membership Fee and Honorary or Life Membership Fee) in the Players table. These will look up the Membership Fee field. You’ll also need to get the Season Start Date into the Players table via a Look Up field.
You can then use a Formula field to calculate the fee required, something like this:
IF( DATETIME_DIFF( {DOB}, {Season Start Date}, ‘years’ ) < 17, {Junior Membership Fee}, IF (DATETIME_DIFF( {DOB}, {Season Start Date}, ‘years’ ) > 65, {Honorary or Life Membership Fee}, {Senior Membership Fee} ) )