I’m not sure exactly what the arrangement is and probably you know this, but Bucharest is not a port. The river that crosses Bucharest is called Dambovita and it is too small to be navigated by cruise ships. Danube passes about 70km south of Bucharest.Typically Bucharest is just used as a transfer destination, and the port for the start of the cruise is on the bulgarian border. Also Veliko Tarnovo is not a port on the Danube, but it’s a nice place to visit for a night or two.
There are no summits close to Bucharest and no summits close to Veliko Tarnovo. There are some summits in the YO/WC region close to the Iron Gates, they should be accessible if you have someone to drive you around. Better get in touch with YO2BP as he is the only one that has activated in that area:
There is a famous rock sculpture not far after the Iron Gates and your cruise will probably stop there, there’s a summit about 2 hours away (on foot).
As for Hungary, I can’t really help with that.
When will you be in Bucharest ?
Razvan M0HZH / YO9IRF.