Shoreboat Service
Yea, they have shoreboat service to Two Harbors from Emerald, but only a few times to and back a day, so you have to find out the schedule. Call on Channel 9 when you get in range.
Otherwise, I would head in the general direction of Cherry Cove and begin to monitor Channel 9 as you get near the shipping lanes. You can then begin to get a handle on availability. If you hear Isthmus is on a wait list, head to Emerald. You can call Emerald Harbor Master when you are five or so miles off to see if anything is available. Then make up your mind whether you want to go around to Cat or anchor in Emerald. If you decide to go around, you haven't lost any time to speak of.
If you decide to go around to Cat, I suggest anchoring on the east side of the entrance on the beach side of the two fish farms. Good holding. The only downside is human powered dinghy. Suggest you call the Cat Harbor Harbormaster on 9 to schedule a ride to shore. If you have a handheld, you'll want to take it with you to hail him when you get back to the dock.
BTW, I have given a lot of rides and towed many a dink in my day, so I'm sure you would be able to grab a tow on your dink going back. Going back in the afternoon is often against the 15ish knot wind that starts blowing around the dinghy docks and moorings 1500 daily. Not so much in the anchorage.
Anyhow, that's my take. Others may have more or better suggestions. Have fun!
PS: give the entrance to Cat a reasonably wide berth; don't cut it close to port going in. There is a rock area there.