damn, 16 DSi's. lucky. where i am the nearest target is a 3 hour drive to the next town, and docent even open until next month.
but yeah, like everyone else said, you might as well just get the SC DS Two. unless, like me, you absolutely cannot stand that useless "plugins" menu on the DS2. or you dont like Alex Rider icon, other than that the SCDS Two is superior.
about DSiware: DSi downloads are stored in system memory, Not sd card, which is limited to maybe 20-30 DSiware Titles. (shantae and mario vs donkeykong eat the biggest chunk), you can transfer individual titles from DSi to 3DS no problem, but you cannot transfer DSi to DSi, and not 3DS to 3DS without full system transfer.
so, you should store all your DSiware on your 1.4.5 DSi, seeing as you allready updated it, rather than purchase DSiware from the 3DS eShop, because its much easier to transfer DSi to 3DS later on.