Charming and Rustic. Looks like a 'Lychgate' -often seen at the entrance to Churchyards- they were used to give shelter to a coffin and mourners prior to a burial service (from old English Lych; corpse). Could come in useful if your family decide to plant you in the wood after you expire? I'm going in mine with the dogs, but hopefully not for a good while.

You may also find a number 28 bus sometimes pulls up alongside it to collect passengers perhaps?
What is under the roof for the little furry darlings to hang from? Huge compliment to your Dads design that they moved in so quickly. Small point; any grief over planning? -could be deemed a permanent structure, albeit for a worthy purpose.
I've read a favourite bat roost is ivy on old trees, good reason to value it, its great habitat.