Speak with Animals does NOT require concentration according to D&D rules. It also is a ritual spell, meaning you can cast it for free by taking 10 minutes to cast it.
So yeah, any of the 3 options are fine. Lasting until the next rest matches what Larian has done with other 10 minute spells and is probably the best option QoL-wise. I'm in favor of it still costing a 1st-level spell slot, since the game is still in need of daily spell-slot/resource management.
