I prefer playing in a concert hall to a church, where it is usually difficult to place the orchestra properly. There are more accidents happening to basses when playing away from a concert hall, I know, I’ve seen them happen. I made it a policy to always look around for a safe place to put the bass when I wasn’t actually playing it. Leaving it on the platform is not safe. The altar, lectern and choir stalls are often in the way so so if it is an important concert the organizers may want to spend money on platforms etc. Of course this may be expensive, and if the church is a small one it will almost surely put the concert finances in the red. A large cathedral is best suited for a temporary stage to be built because there is space for a big audience to justify costs.
Outdoor concerts, for me,were a bane. I remember on Hampstead Heath in London there was a permanent stage with an overhead canopy situated in front of a lake. It was OK as regards adequate seating for the orchestra but the mosquitoes were terrible. One had to take an ample supply of bug screen, but somehow or other one of the little pests would always bite. Then there was the wind. I always took some clothes pins along so the music would not disappear in a sudden gust. You had to be careful of the bass as condensation appeared on it by the end of the concert, so I always gave my bass a good rub down and put it back in its case as soon as possible.
Just before the concert, the impresario would always say to us “Don’t hope for rain boys, it never rains for me”. He had been putting on these concerts for years and Fate was kind to him, it never did rain.
When I was playing with the Vancouver Symphony Orchestra there were always concerts given on the top of Grouse Mountain which were well attended, but the orchestra still had to cope with bugs and gusts of wind. Too, there was the cold to consider and I always put my bass in its case as soon as possible even in the interval because it may be expensive if some repair patches become unglued and you have to take your bass in for repair, possibly having to have the belly removed.
Faced with costs like these it may be better for you to turn the date down and only accept dates in regular concert halls or own a second, cheap instrument and use that.