As legal guardians, you are entitled to the exemption for your grandchild, but only one of you can claim it. Decide who should do this; it depends on who will save more in taxes for the family. You do not apportion the exemption between you.
Depreciation methods that allow faster write-offs than straight-line rates in the earlier periods of the useful life of an asset. For example, in the first few years of recovery, MACRS allows a 200% double declining balance write-off, twice the straight-line rate.