TBH, I would see going to a public PS and then Trinity for HS as a compromise.
Trinity is a great school, but like any private school (particularly the COE ones) completing one's entire schooling there can be a very sheltered experience. From the religious POV alone, the exposure to many more cultures and kids at a public PS will give her a broader view; whereas being in the school her entire life will make taking any other road more difficult, itms, I can totally understand why your DH feels reservations about that.
Plus, the fees for 13 years at Trinity would be astronomical! Could it be that is a concern playing on his mind also, but the religion is just another?