I think for these kinds of jobs, you aren't really paying for the "service" or the time involved in that service, you're paying enough to make sure they feel really compelled to do the job and not resentful of the time it takes. I used to housesit/petsit when I was single and felt like sometimes people thought they were doing me a favor by giving me a change of routine. They didn't seem to realize that it was a pain for me to change my routine, pack up my stuff, have to run to their home to let their dog out when I would have normally gone out with my friends straight after work, etc. I finally stopped doing it because it really felt like I was being used.
My son is only 14, and we've settled on $15 a day when he petsits the neighbors animals. It seems ridiculously high to me if you think in terms of hourly pay. However, he visits them 3 times a day, feeds and cleans up after them, and plays with them. The price becomes an issue, not about those things, but about the fact that he often has to rearrange his schedule, skip social opportunities like sleepovers, etc. (or negotiate with a family member to take his place) to do so. The price is because he is responsible for those pets and if they get sick or need extra attention he'll step up.
I would skip the care package stuff pay him a flat $10 per visit. Cash is way more tangible so even though it might work out the same, it may feel different.