Well, these are just my opinions if I was in the same situation, hopefully others will have a variety.
As far as the AP for the first activity, I see two different options. The first option is to count it as light. For me, I would not want to accidentally give myself points I did not earn. Just remember, though, regardless of how many points you assign, you did the work!! The numbers are not as important. I used to worry so much about forgetting to enter a glass of water or such from days past. But the effort is much more important. Does that make sense? (Although the effort may not seem as important if you have 2 points at the end of the day and are eyeing that 3 point ice cream hehe). The other option is to check next time if you can sing while doing it. Not sure where you walk, but hey singing with the kids will probably make it easier anyway, right?
Personally, I would keep them on alternating days. Just for me, when I start something where it is rest a day et cetera, I usually rest a day and then another day and another day. . . :-p
Wow! 28 points a week would be very hard for me as well. I only get 2.7 for an hour and ten minutes of walking. I guess I could bump part of it to jogging or such, but would have to add more caffeine to my day.