se before a

Hola Will 

You need "se" there because "le" as an indirect object pronoun turns into "se" if there is also a direct object pronoun lo, la, los, las, which is this case: quiero regalárlelas > quiero regalárselas

But here's a Kwiziq lesson on this specific topic where you can see more examples and explanation. 

Saludos cordiales

Inma