As jess_hawk said you can fix those holes a bit later, but I don't know if I'd call it seaming. A while back I made a little sweater with quite a few little intarsia boats in the yoke and it looked pretty bad until I fixed in the ends and then it looked fine, so don't despair.
If you are real worried and don't want to work the whole blanket before you see how it will turn out, when you get a ways past a change try working in the end in a way to heal the hole and see how you like the result. I don't know if there are any tutorials or videos anywhere about how to do it. I always feel like I don't know what I'm doing, and just do what seems to need to be done to close the hole and it works out okay.