The reopenings of the river attractions, Tom Sawyer's Island and DLRR are at the mercy of the construction schedules. Currently, the attractions affected are scheduled to come back in early April of 2017. There is some padding in the construction schedule, to give extra time, but delays do happen. I think if you do want to go to DL and experience the full park without SW being open, you should be safe in late April or May, but I'd keep an eye on the forums to see what's happening. If you want to see the new Guardians overlay at DCA, you would want to wait until July. The only other question mark is what attractions may be down for normal maintenance you may want to see. Make sure Pirates is operational and Haunted Mansion, Matterhorn, Splash and Space. If Fantasmic is important to you, check Fantasmic's schedule also. The majority of the attractions affected by SW construction should be back in April though, if everything goes to schedule.