The bridal couple and reception hosts should get to the reception as soon as possible following the ceremony. People do expect some delay, but any longer than thirty to forty-five minutes becomes excessive, unless your invitation included a later starting time for the reception.
The usual hold-up is photographs. Plan the photo session so that the shots including parents, other family members, and attendants are taken first, both at the wedding and reception sites. Be sure that your photographer and wedding coordinator are aware of your photo schedule. It’s not acceptable for the wedding party to disappear, whatever the reason, while reception guests are left to cool their heels and wonder when the reception will begin.
If there’s a long lag between the arrival of guests and the wedding party, arrange to have special helpers at the reception site ready to greet guests, make introductions and see that guests are offered drinks and hors d’oeuvres. It’s nice to have some music (live or recorded) to set the mood.