I wish I could help you on how to book into attractions, my friend is not that long back from Rome,she didn't mind the queues, have an idea of what you want to see, not too many fountains or churches and the like of even old sites like the Colosseum, there's just so much, you can get one of those tour buses - hope on hop off sightseeing tours. Whatever you do, don't put your feet in the fountains, it's a €240 fine since a few months ago. I hope someone can help you better, my friend is at work now but I'll ask her what she thinks later.
Enjoy it, she loved it and is planning a return visit
http://www.telegraph.co.uk/news/2017/06/12/tourists-wade-romes-fountains-hit-212-fine/