Not a city break, more a spa/pool type thing if those exist? I'm guessing not, but I can try. Toddler is fairly laid back and wouldn't need lots of other entertainment apart from the pool & even better a kids club. Ideally not butlins type thing as I wouldn't enjoy that (not without lots of booze!) and they are still too young to appreciate it properly.
I can't afford a proper holiday and have no childcare so was wondering if a UK hotel with a pool might be a comprise?