I have no idea what you mean by "omnipresent in heaven," though. The term is self-contradictory.
“If the saints stand in the presence of God in heaven, they obviously know whatever he wills that they should know. We can’t place any limitation on their knowledge, only He can do that.”
Keep in mind that your church does not teach that Mary and the Christians in heaven are receiving a prayer via transmission from God. It teaches that Mary (as an example) is actually present with the believer since she is somehow sharing in the divine attribute of omnipresence.
“Mary is taken up body and soul into the glory of Heaven, and with God and in God she is Queen of Heaven and earth. And is she really so remote from us? The contrary is true. Precisely because she is with God and in God, she is very close to each one of us. While she lived on this earth she could only be close to a few people. Being in God, who is close to us, actually, “within” all of us, Mary shares in this closeness of God. Being in God and with God, she is close to each one of us, knows our hearts, can hear our prayers, can help us with her motherly kindness and has been given to us, as the Lord said, precisely as a “mother” to whom we can turn at every moment. She always listens to us, she is always close to us, and being Mother of the Son, participates in the power of the Son and in his goodness. We can always entrust the whole of our lives to this Mother, who is not far from any one of us.”
“Papa” Francis speaks of the “spiritual presence” of Mary:
April 28, 2013
Regina Caeli
“I would like to entrust the confirmandi and all of you to Our Lady. The Virgin Mary teaches us what it means to live in the Holy Spirit and what it means to welcome the newness of God in our life. She conceived Jesus by the work of the Spirit, and every Christian, each one of us, is called to welcome the Word of God, to welcome Jesus in ourselves and then bring him to everyone. Mary invoked the Spirit with the Apostles in the upper room: every time that we come together in prayer, we are supported by the SPIRITUAL PRESENCE of the Mother of Jesus, to receive the gift of the Spirit and to have the ability to bear witness to the risen Jesus. I say this in a special way to you who have received Confirmation today: may Mary help you to be attentive to that which the Lord asks of you, and always to live and to walk according to the Holy Spirit!” (Pope Francis, April 28, 2013
Regina Caeli, Capitalization mine)
Furthermore, this also implies that Mary and the Saints must have all knowledge about the individual praying, as just “hearing” the prayer would not work. As you need to know the “heart” as to whether or not the prayer is truly being spoken righteously. Not to mention one would need to know all the languages of the world, the personal circumstances of each individual, etc.
When I said “omnipresent in heaven,” what I meant was “omnipresent after death,” and omniscient also. Since it is not possible for a human spirit, or any spirit other than God, to be in more than one place at the same time, and to know all of these things.
Instead of imagining such complicated fables, it’s easier to just stick with the scripture, which ascribes all prayer to the Almighty, and to none else.
Angels are the ministering agents sent to minister to those who inherit salvation.
Hebrews 1:14 Are they not all ministering spirits sent out to serve for the sake of those who are to inherit salvation?