the minhagim of Ger are restrictive in a certain way for non-gerrers, however most gerrers in the US do not follow in those ways, and many in EY dont either.
chances are, if he is a good bochur, he probably does not even know of these chumras- it will depend where he learns his halachos, what he will hold.
Be happy for the couple. Gerers have no less shalom bayis with thein HanHagos.
To think of it, The Yeshivish people have more hanhgas then balay Batim, such as day 31, Or Ohr Zerua, should you tell them? this is the fact of life. The Yeshivish are just as happily married then the bali batim, or the MO that have less halachals!