A Lizardfolk Ranger with the Ancestry Feat Bone Magic. He has +2 Wisdom and +0 Charisma modifier. He chooses Puff of Poison as his innate cantrip granted by Bone Magic. Bone Magic does not mention any specific modifier to be used as Spell DC, so the innate spells rules apply and charisma mod is used - resulting in a spell dc of 13 and 0 initial damage.
The Ranger class details say
Your warden spells are primal spells. When you first gain a warden spell, you become trained in primal spell attacks and spell DCs. Your spellcasting ability is Wisdom
I conclude that if said ranger does not have a warden spell, his innate cantrip would work as stated above. But if he would chose a feat that gives him a warden spell like Gravity Weapon at level 1 or later on his spell attack and spell DC would change.
Is this correct?