Perhaps

Personally, I think a couple should have only two children in their household at a time.  Any more ought to be sent to stations out outside of Sparrow lands, and return only briefly for visits.  They could also bring organic matter to increase the fertility of the Sparrow lands such as compost.  Also they could bring back gifts for their family.  As such the entire clan will benifit from their service.    

Perhaps Sparrow's Gempukku would be to defend the Kaiu wall for a year with the Hiruma Scouts.  Before they were sent to the Hiruma they would receive a blessing by a priest.  During this time they were with the Hiruma peasant weapons to fight such as the sling.  Their relatives should gather while they are doing this to have a prayer vigil.  Upon they're return they will be given a ritual cleansing to help cleanse them of any taint they picked up in with the Hiruma.  Then they would be presented their swords.  Then sent to their stations.

Perhaps the Dragon clan could use Sparrow Bushi to defend the Northern Towers of Flame.  Additional bushi would be useful there to them.  The Dark Oracle after all keeps sending his minions there.  Perhaps the sparrow could setup a base with the Ronin at Nanashi Mura, for helping to defend the Northern Towers.

Perhaps the Sparrow could staion troops at Oiku.  Then if they would move with Lion clan to defend Toashi Ranbo if necessary.  Then the Lion will have more bushi on there side.  Also Sparrow bushi could be stationed at the Kitsu Tombs.  If the Tsuno attack they may prove most useful.  Also they could help in minor duties.     Perhaps some Sparrow's could be snet to Ninkatoshi.  They may prove useful in an event of an attack.  Also Sparrow stationed at Toshi No Meiyo Gisei would be useful in an Tsuko attack.  Another place that Sparrows could be stationed is Shiranai Toshi as they could help provide order.  Foshi could also use the Sparrow to against the Phoenix and Tsuko.  Shiro No Yojin may have need of Sparrow to maintain the estate, as well as defend it should the need arise.  Also Sparrow's could be stationed at Beiden's Overlook.  However, only the most experience Sparrow bushi would assigned here.  Perhaps the Sparrow and Fox could station some bushi at Rengai Torid-e and Kokoru Nezuban Mori.  Wood is a needed commodity to the Lion Armies, and Foxes are some best woodsmen in Rokugan.   

Works of art could be sent to Shiro Akodo as a good will gesture.  Perhaps the Lion would let the Sparrow use Shiro Shimazu in exchange for their service.    

Perhaps the Sparrow could station Bushi at Kitomihari.  If the Yobanjin tribes are amassing for war they may prove useful.  Also Sparrow bushi could be stationed at Zumiki-mihari as well.  Perhaps Sparrow bushi training with the Phoenix could be stationed here or completing there obligations.  Then

Perhaps the Unicorn could use Sparrow bushi stationed at the Watchtower facing the River of the Unexpected Hero.  Incase of a Shadow clans assualt they may prove useful.  The sparrow could also do combat maneuvers with the Unicorn.

Perhaps Yasuki Hachi could use Sparrow's to maintain his estate.  They could also help defend the castle in an event of an attack.  Then the Sparrow's may be of use to him.

Perhaps the Sparrow could build a port and a Sparrow Merchant Marine Academy built at Kiken and Roka/Ryu Bannin Toshi.  The descendants of a child who gave a dragon a riceball, may wish to join the Sparrow clan.  But first sufficient funds must be acquired.  The Turtle, and Mantis ships could be given access to this port.  Also the Lion, Phoenix, and Crane, may find it convenient to have a market for their products.  The Merchant Marine fleet could practice aquaculture.  Also excess food could be sold fish could be sold to the highest bidder.  Perhaps the Sparrow's could use the Imperial Storehouses that stand empty to store fish in.  Perhaps special permission would be needed for this I do not know.  But I indeed think it a waste that they stand empty.  Perhaps the Crane would like more defenders for Kosaten Shiro.  The Sparrow clan could station bushi there.  Perhaps if exchange for providing bushi the crane may help build an school there.  Also the Mantis may find it useful to have Sparrow bushi at Kyuden Ashinagachi afterall the Scorpion still hold great hostility there towards the Mantis.  Perhaps they too they could help build a school there.