cake experts: I need some advice pls

[vannah]

On how to incorporate a new ingredient into a cake mixture : I bought some milled linseed and sunflower seed mix and wanted to get some of this into a basic cake mix for my son as I've no other way of feeding it to him (he has some health problems )

If I add it to cake mix, do I take out flour for the quantity of milled linseed mix?
Will it make the cake dry or dense?

Any tips appreciated

I would add it right to the cake mix and not make any substitutions. Some recipes use ground flax as a replacement for egg (when mixed with water) but dry, I think you should be able to just add it in. That said; I'm picturing a small quantity...how much were you thinking of adding?

No idea how much to add! Thanks though, will try it like that