Jul 11, 2015 - 5:30 PM
Welcome to MySwissAlps, Crina!
Yes, a rail pass is certainly a good choice. I think you should look into a Swiss Half Fare Card. It gives 50% off pretty much all trips, including mountain transportation. Your child will travel along for free. If you want to make a detailed calculation to make sure which pass is most economical, you can follow these guidelines.
Both Grindelwald and Wengen are great for a family holiday. They're situated beautifully, right at the base of the gorgeous mountain range. Grindelwald is somewhat larger, thus providing more services, and more touristy. In my view, you can't go wrong with either choice. This matter has been discussed in previous topics that might be interestig to you. Some examples:
I hope this helps you prepare for your trip!