Absolutely. They way convoke is worded tapped creatures can pay for or 1 mana of their color so just like you say tapping 5 creatures (minimum one of them has to be white of course) will make Venerated Loxodon practically free, but technically his CMC will still be 5 as normal, in case your opponent wants to Disdainful Stroke it.
October 9, 2018 5:36 p.m.
Yes. As long as at least one white creature is used, you can cast Venerated Loxodon using entirely creatures. Said White creature doesn't even need to be mono-white. Progenitus would work just the same as an Eager Cadet would.