I think the Mercere I play, would offer as a initial offering two years of service for every proven Gifted child produced. On top of that he would also offer, because of his place as a ships captain, free transportation as long as the direction is within reason of his own, for life.
Would also sweeten the pot by offering maybe a Mercere discount to vis transactions... depending on how my magus could work the exchange rate or what have you.
I think the House as a whole would possibly react two ways. Maybe they see such a Fertility worker as a blessing and they completely begin funding that mages entire existence as long as the sorcerer can turn out say one Gifted child every three years?
Or maybe the House doesn't want more magi? Maybe the Redcap leadership sees the Gifted members as unique but annoying figure heads. Maybe like the royalty of their house, but a post-parliament royalty, expected to shut up and look nice and say what they are told to say.
Like I said though, my character, would be very positively inclined to buy the benefit.