I stay at home with two little kids. When we hit that 2 p.m. slump, mama is ready for everyone to be napping! Even if I just need a couple of quiet hours to call and make appointments, wash the dishes, shower, or just sit in silence. Unfortunately, now that my oldest is 4, he has decided naps are not for him. So. Rude.
Quiet Time
This is a popular one for a lot of mamas (myself included) and there's a reason for that: it gets the job done. Once your child wraps his head around the fact that not having a nap does not mean he gets to run around the house, but instead, he will have to let his body and mind take a rest, this is super effective. Whether he's in his room hanging out with a few books and a coloring book, or in our situation (since sis is sleeping in the kids' room), playing in the family room with quiet toys, your little works on staying calm, quiet, and you still get to enjoy a little bit of peace. I also let my son know that it's independent play time--this is not the time of the day to ask mama for every single thing. I set him up with a drink, a snack, and some of his fave quiet activities. Then mama gets some time to sit/lay down, rest her eyes/read a book/watch a show. Most of the time, this works great for our little guy!
Screen Time
Say what you want, but this is a crowd pleaser in so many ways, and I am a freaking fan. Just don't tell my kids' pediatrician. When you're at home with your littles all day, doing the most, running around, picking up after spills and messes and kissing owies and breaking up fights, you need some time to not think about a single thing in this world. So... the TV or iPad or tablet is your friend, mama! Get your little one set up in the family room with a blankie, a snack, and a quiet movie, and let them know this is his/her time to watch a show. This is something my son does (normally on the iPad) and he is usually able to be really independent on there. We also have a couple educational games on the tablet that he loves to play, which helps keep our high-energy boy engaged in something, but still quiet.
Mama's Bed
This is probably my favorite thing to do with my little guy when he has completely given up on napping in his room, and that's to bring him to mama's room and have him take a nap in my bed. This doesn't happen as often, because my son is pretty much go-go-go from the minute he wakes up to the minute he sleeps at night, so napping with me isn't that easy for him. But I will normally turn on some quiet music or the white noise machine and do my best to let him fall asleep. At the very least, I'll get about 30 minutes of quiet snuggles before he decides he needs to resort to option 1 or 2, but every once in a while, this one works, and it's downright heavenly, mama.