Are you suggesting that God (Christ) is not omnipresent?
Omnipresense and Real Presense are two totally different terms.
If you want to abuse the idea of omnipresence that way, then why do you need a church? Just partake of communion by going out to your back yard and eat a fistful of dandelions, knowing that our omnipresent God is present in the dandelions.
OR, realize that "Real Presence" is more specific than "presence."