We will be in Prague next week and are looking for points of interest and interesting activities while we stay there. Our hotel is in the center of the city. This is for my 50th birthday and my wife is 40.

My girlfriend took me off to Prague for my 50th earlier in the year and we had a great time, although we weren't that near the city centre. I'd get a hold of the Lonely Planet city guide to Prague as it's got a load of useful information in it regarding attractions, bars and good places to eat either at night or during the day. Although we used it for reference, we didn't rely on it as we preferred to find places and attractions as we wandered around rather than having set plans.
Charles Bridge at dawn is magical, even when it's as misty as it was in February - the people appearing out of the mist as they walked over the bridge was quite ethereal. We walked everywhere whilst we were in Prague and just made sure that we kept our passports, cards and currency well hidden when we were wandering around either at night or during the day. We did have one disappointment in the commercialisation of one of the more recent historical sites in Prague - people handing out free cans of cola in a square associated with Czech freedom seemed rather crass at the time.
For the most part we ate well and at a reasonable price at all bar one of the bars/cafes/restaurants we ate out at, but one of the better cups of coffee (ie large, hot and very necessary after dawn at Charles Bridge) was in the (then) newly opened Starbucks. Only visited this twice, as the rest of the time we headed for locally owned establishments.
One of my work colleagues was taken over to Prague by his wife last week and he thoroughly enjoyed his three days there. Carrie and I will be back to Prague when we can, but this time it will be in a more central hotel. Ours was good, but the walk back to it reminded me of the walk back to my flat when I was at university back in the 1990's... Interesting is the best word to describe it. Keep and eye on the weather forecast before you go though - we were pleased that we took our down jackets over with us because it was rather cold in February... Have a good trip!