A 4:
No drawback to doing so is listed in the entry for the item. I suppose that, while animated, it might be continually squirming in place, or the like, which might be awkward in some situations, but even that is speculation, and still leaves plenty of time for it to be animated in advance of when one would want to use it.

A 5:
An ability check is not an attack roll, even if it's for an option which takes the place of an attack. By the same token, you would get advantage from things that help checks but not attack rolls, such as the Enhance Ability spell.