Tattoos are allowed for both goats and sheep, and can replace ONE of the eartags. Also you can use leg straps on goats (however the size makes it best used for adults only as kids legs are still quite thin). However you will still need one eartag, so the coombo of tattoo and leg strap is not allowed.
I only tag my kids before they go out first time for a show, and only 1 eartag, which is (as far as I know) all that is needed until they are 1 year old.
Don't tag your kids until you absolutely need to...