As far as I know you won’t be able to do this with Home Assistant at the moment. Therefore I suggest Home Assistant Container or Home Assistant Supervised (see the different install methods here) and run your audio in to google speaker separately from HA on the same machine.
However as Mutt said, the Pi 2 is not recommended and you’ll probably hit limitations quickly. I’d either get a separate Pi 3 for HA and keep your audio in to google speaker on this Pi or get a separate Pi 4 and do everything there.