I know what you mean about only being able to sleep in a crib. We took our girl camping about 2 1/2 months agao in a small tent (no room for pack-n-play) and it was a complete nightmare. Just came back from another camping trip with a nice big tent and a pack-n-play. Though it was not completely smooth-sailing, it was a million times better.
As for going to dinner, we bring the pack-n-play with all her bed-time acoutrements (comfort items, bath items, books, etc.), do the whole routine and put her to bed in the quietest room in the place. This often works quite well. Then we scoop her up when we're ready to go, put her gently into the car seat, and move her gently to her crib when we get home. She often wakes up a little for the car ride, but is completely quiet, like she's sleeping with her eyes open. But this only works if we stay for a few hours after she goes down, so that she's in a real deep sleep. Since DD is so big, we have no dream feed. But I think I would try to get home in time for the DF, do the DF, then put your lo to bed. It would probably disrupt the routine the least.
Now, getting my girl to take naps in the pack-n-play is another matter. Sometimes she goes down great, others only after 45 minutes of talking to herself, sometimes not at all. I get frustrated, too, but I really try to take it in stride. After all, we have to go out sometimes. Otherwise I will go crazy, and my family would make their displeasure known if we stopped visiting.
As for errands, at this age I can schedule errands for A time and my girl will stay awake. But when she was younger, she always felll asleep in the car and often in the stroller. So then I would try to schedule car rides and long rides in the stroller for the end of A time and beginning of S time. Of course her naps were never as long or as restful, but do what you've got to do. Figure out a way to give your lo the longest stretch of the best sleep you can.
HTH!