Good choice. You have a reason for going there, both family and honeymoon. While I’m sure that the dollar is very weak there – it’s not an overly expensive place (I would guess) compared to London or Paris. We went to London for new years year before last and stayed on the Thames next to the London Eye. It was brutally expensive. I couldn’t imagine what it would cost today. Even a starbucks latte was about 7$ back then. I felt like a third world citizen, couldn’t imagine what it would be like now.
I’m sure that Prague would be cost effective and fun – enjoy your trip!