Seems high for the house size but I'd need a lot of elaboration on the quote to see how unreasonable this is

How many heads? What brand/model? Is there electrical upgrade work needed (panel replacement). What's the siding on your house (masonry could raise the price a bit).

I usually recommend getting at least three quotes for large projects like these.

Also, it might be worthwhile asking your homeworks auditor if they are still offering rebates on integrated systems. This would integrate your mini splits with the steam boiler so you would use natural gas when the outside temp drops below the optimal level for the mini split