I am a tabletop wargames rules writer (Ancients/Medieval/Renaissance). I have also previously written DOS-based wargames campaign management systems in C++, but not for several years. I am about to retire from my day job, so the time is ripe for a major project.
I want to write an updated multiplayer historical wargames campaign management system. The player interface needs to be web-based, but the server end program (of course) does not. The whole system will need to be customisable so that campaign-masters can set up their own campaigns in any pre-20th century historical period.
I am seeking advice as to the best programming languages/platforms to use. There seems to be a fairly wide choice and I have little idea how to choose between them. I have experience with Basic, C and C++ (oh, and machine code

), but learning a new programming language is not a problem.
Previously I have programmed my data structures from scratch, I am not sure whether using a database language would be helpful - I don't need query facilities, but easy customisability of data structures for end-users designing their own campaigns using the system is important.
Has anyone got any advice as to which platforms/languages I might best use (1) for the web-based front end and (2) for the server-side program?