I LOVE the Wii Fit Plus! It's got a great variety on there! You could do some of the yoga while you are pregnant. Your husband could do the strength training. And all of the games are fun! There's also aerobics on there that can really work you out! I've been doing my own routine of the strength training for a week now and I can absolutely tell that it is working. I'm trying to get ready for snow skiing! You can also do multi player with some of the games where you take turns for as long as you like to see who can get the higher score. When you are playing from your own profile with any of the activities tho, it saves your score so you can also compare scores and challenge each other!
The My Routine is a great feature. It makes your workout go much quicker if you are just wanting to do some personal training. This is what I've been doing. I selected the strength training activities I wanted to do and it goes through them one after another without you having to stop in between and click buttons to tell it what you want to do next.
As far as the pricing, the Wii Fit Plus with the balance board is $100. A new Wii remote (not the nunchuck) is $40. But you can also get used stuff from places like GameStop.
As far as other games, it depends on what you like. There is also the WiiWare that you download straight to your system (if you have wireless Internet access). Some of those games are only $5.
Ordering online with coupons is another way to save. http://www.dealnews.com and their coupon site http://www.dealcoupon.com are a great place to find deals and sales on things and coupons to use. You can sign up free to be alerted when they post any deals with the keyword "wii". Then they email you as soon as a new deal is posted! Not too long ago they had the Wii Fit Plus for $70. But that deal has since expired...
Feel free to ask me any other questions about the Wii. Only other games I have are Mario Party and Animal Crossing, and the WiiWare "Learning with the PooYoos" for my daughter!