In theory that would work fine. Two 10W LED auxilliary lights will draw about 1.5A, so they could quite feasibly be tapped directly into the feeds to the high and low bulb holders and use a common earth. However, it would be better practice to use the tapped feed to trigger a relay (or two) and run a fused supply direct from the battery to the lights via the relay. This obviously involves more wiring time and you've got one (or two) relays, plus fuses to stash somewhere.

There are many ways to skin a cat though! A lot depends on how fussy you are about things?

Do you intend fitting any switches to the auxilliary lights so they can be isolated/turned off?

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