We had a 4 day/4 night family trip planned in June 2017. My father purchased an annual pass for the AP hotel discount (you can check the discount at UOR before purchasing the pass). For an extra $120 on the ticket, we saved about $400 on the hotel so $280 in savings. The cheapest AP available to us was the Power Pass + a single day VB ticket (no one is a FL resident and we were planning on spending 1 day at VB). The rest of us bought 3 park/4 day park to park tickets. We were originally going with the Power Pass for the hotel discount; however, ended up purchasing the Preferred Pass specifically for the in park restaurant discounts. We had 5 people dining over 4 days (including the more expensive HP places and table service). The Power Pass only includes a few restaurants at the resorts (see my later post). The price difference between the Power Pass and Preferred is $40 and we saved more than that in dining discounts, but your mileage may vary.
Plus, my dad visits his mom in FL every year so he was able to use it again in the year. They usually go to WDW, but he wanted to take her to WWoHP anyway so it worked out.
Some of the passes have parking included (or discounted parking) so that benefit can be used for your whole family. We were staying onsite so didn’t use it on this trip, but my dad did use it when he returned with his mother and they stayed offsite.
I have no idea about upgrading a multi day ticket to an AP.