Kids certainly are not the only ones who need to keep warm. I recently heard an excellent viewpoint that if parents are warm and happy, their attitude will help keep their kids positive too. The truth is that kids don't miss a thing, and if you are cold and frustrated, your kid will certainly follow that example (even if they are perfectly warm!)
A couple of our favorites when it comes to adult base layers:
Icebreaker New Zealand Merino Wool
...makes long underwear for adults too (and yes, it is just as amazing as the smaller "kid-version". Mountain Papa and I both have a set that we wear constantly. I already spoke a bunch about Icebreaker the company in this post, but I wanted to highlight the pros and cons we see of Merino Wool (and particularly Icebreaker.)