Yes, the guilt can be ridiculous at times! I think it's just a phase of the relationship, where we're not really NRE anymore but we're still concerned that everyone's feelings are constantly 'positive'. Which is crap, because in what relationship is every person happy all the time??? Not in any mono relationships I know! So why such high expectations from a poly relationship?
I think now is definitely the time to start thinking about nurturing the relationships within the relationship. At first my gf was resistant to this idea too. She felt like 'why do we need to do this?' But once we started she became the biggest proponent of date night. We now try to get each of the 3 couples a date every 2 weeks. This works out to 4 dates a month for each of us, which is quite ambitious given we have a 3 year old and each work a full time job!
It really does bring a nice energy to the relationship, plus it gives us one on one time our kid to do something special on the nights we stay home.
I've grown much closer to my husband through all of this, because it gives us alone time. I've also grown close to my girlfriend, this time lets us foster our sensuality without the testosterone in the mix, if you know what I mean.