、。
The son of that shop is going to have a shotgun wedding with a local girl soon.
Literal
There-over [gen-の] shop [gen-の] honorific-son [subj-が], this-time this land [gen-の] girl [with-と] 'already-happened' marriage [obj-を] will-do [fate-ことになっている].
息子さん 'son' with the polite ~さん is the respectful way of referring to someone else's son. 出来ちゃった結婚 (literally 'the it-has-already-happened marriage') is the slang name for a shotgun wedding — 出来ちゃった is the casual contraction of 出来てしまった, '(a baby) has already happened.' The full phrase is often shortened to デキ婚. ~ことになっている marks an externally determined or socially scheduled future — 'it has been arranged that X.'