Prague is good fun, check out showpark!!!
When did you last go? Things have changed dramatically in the last couple of years. One of the Show parks has closed, and reviews of the other aren't encouraging.
Prague is still worth visiting, but you need to do your research before you go to avoid the tourist ripoffs. Also lots of SPs and establishments have limited availability at weekends, especially Sunday, so not sure I would recommend it for a weekend trip. You certainly wouldn't be getting the best.
TBH, for punting, in terms of availability and value for money, I still think London is hard to beat. Particularly when you factor in travel and accommodation costs, and time wasted in travelling rather than punting. Just not as exotic as Spain say.