Both options work; it depends on priorities.

Swiss Travel Pass:
- Trains are very reliable.
- Kids often travel free or discounted with the right pass/age.
- No parking or speeding worries.
- Very convenient if you stay near main stations (Zurich, Lucerne, Interlaken, etc.).

Car rental from Zurich:
- More flexibility with timings, stops and luggage.
- Good for kids’ naps and spontaneous stops.
- Driving is easy and scenic.
- Downsides: expensive parking (especially in Zurich) and very strict speed limits with high fines.

If your plan is mainly city‑to‑city and you’re staying central, lean towards the Swiss Pass. If you want smaller towns, viewpoints and maximum flexibility with kids’ schedules, a car can be worth it (budget for parking and drive carefully).

Near Zurich with kids, Swiss Science Center Technorama is an excellent hands‑on option.