The chatan and kallah's keriat shema and hamapil on their wedding night should not differ from other nights.

There are two possible times to recite them. Ideally, after intercourse one could wash one's hands and then recite shema and hamapil (or hamapil and shema, depending on one's custom) prior to sleep. On the wedding night, the couple usually gets up anyway to separate.

In general, it is also permissible to recite them before having relations, particularly if you might fall asleep and forget to say them afterwards. Hamapil is considered a birkat hashevach (a blessing of praise to Hashem),and some interpret the line "utehi mitati shlemah lefanecha" as referring to the intercourse which follows and not just to sleep. Even though the usual custom is to not speak after hamapil, in this case you should not hesitate to communicate naturally with each other.