If you're not sure how he'll feel about it, why don't you just ask him about it? Rather than waiting to see if he does anything, or arranging a surprise - Just say something like "What do you think about doing something special for our two year anniversary?" The two of you could plan it together. Celebrating two years is a lot different then celebrating every single month! Besides, it's a good excuse to have a really nice date night and I'm sure he'll appreciate that.