Start with the Monkey Forest — it costs a fifth of the zoo, sits in Ubud town, and the monkeys are wild. Just follow the rules: nothing in your hands, no sunglasses on your head, no food anywhere on you.
Pick Bali Zoo for a structured family half-day. Its strength is proximity to Ubud and close-range encounters; its animals and grounds are decent, not world-class. The evening "night zoo" sessions are a fun twist if your days are full.
Pick Bird Park if anyone in the family loves birds — the free-flight amphitheatre show lands with all ages, and it is calmer than the zoo on crowded days.
Skip Turtle Island unless you are already doing water sports at Tanjung Benoa; it is a small pen-based stop, not a wildlife experience.
One practical note for all of these: carry small cash. Ticket counters take cards, but parking attendants, sarong rentals and drink stalls outside the gates are cash-only, and ATMs near the Ubud sights often charge steep fees.
Compare with the full-day Bali Safari option, and slot animal stops into an Ubud driver day via Bali sightseeing tours.