Christi -
I want to point out that your son's school already seems to take providing above level instruction to your child as a matter of course. (sends home 2nd grade LA)
this is a very positive sign, as the past provided the surest projection of the future - perhaps the immersion class WITH individualized study -EPGY math and LA from upper level classes, or even EPGY's language arts classes on the "English Language Days."
Or perhaps they will allow you to send your son on the Spanish Days and homeschool on the English Days? This might be the best of both worlds, as the immersion Spanish seems too good to at least try.
I do like to say yes to gradeskips as early as possible, but I think Spanish immersion is worth staying for, at least for a year or two. Here's an idea: Spanish Immersion on the Spanish days, and 2nd or third grade on the English days. That way your child get the considerable advantage of a 2nd language plus the social benifits of making friends with a group that may be more likely to be intellectual peers. This would be very taxing from an organizational point of view, but, depending on the personality of your child, a teacher who is comfortable with individualizing the curricula through compacting may be able to make it work.
Sad news is that Elementary school isn't a good fit for many of our kids, but there are skills that need to be gained, sooner or later.
My main advice is to forget about the grand plan - try to find something that works for the next 6 to 12 months. Look for flexabilty from school personel. Take as good care of your family finances as possible - you are right about these kids being expensive! Remember that it's not your fault that your child has different needs AND it's not your fault that there isn't any clearly marked path for you to follow. You are a pioneer here.
Best Wishes,
Trinity
