You might look into a new, or used Half Pint. I spent one year on cinder blocks , then two years with a Half Pint, and the last ten on a Leader 2x6.

We made some great syrup on the Half Pint and sold it for nearly what I paid for it.

With a growing family; it sounds like your time is worth more than the $900 or so you'll save building up an oil tank arch.