You can expect to be welcomed! The Church welcomes all to its sacramental celebrations. As a witness to the marriage of the bride and groom, you are called to actively assist in the wedding ceremony through words and actions that show your love and support for the couple. If you are not Christian, this may be as simple as being a warm presence for the couple and participating in the words and actions of the wedding liturgy as you feel comfortable. (No one expects you to say prayers or make statements of faith that do not reflect your beliefs.) If you are Christian, you are invited to join the whole assembly to offer your prayers (spoken and sung) for the couple.
The wedding liturgy, called the Order of Celebrating Matrimony, will include Mass. The Catholic sacrament of marriage normally takes place within the context of Mass, because the Eucharist/Communion both reflects and strengthens the bonds of love between the bride and groom, and between the couple, the Church, and Christ. Because Jeriah and Silvia's wedding will be celebrated as part of a Mass, it may last an hour.
You may be wondering whether you should come forward to receive the Eucharist when everyone else lines up to do so. The short answer is that only Catholics should receive the Eucharist. Another name for the Eucharist is Communion, because the act of receiving it both reflects and effects the spiritual union of the believer with Christ and all the other faithful. In other words, it's a statement of Catholic faith, one that you probably do not want to make if you do not share that faith. Those who do not wish to receive or who are not accustomed to regularly receiving the Eucharist at a Catholic Mass may either remain seated during the Eucharistic procession or may join in line and cross their arms to indicate they would like to receive a blessing.
Children are welcome at the ceremony, but unfortunately , the reception is adult only.