I raise multiple Tamagotchis at once even if they're hatched at the same time but I do make sure this is during summer break as they constantly need care during the baby and toddler stage. If you don't have time or have a hectic schedule, I don't recommend running more than two Tamagotchis at a time.
The thing I do is check on them time to time. If they're hungry, feed them meals. If they're unhappy, feed them snacks. Don't play with them that much 'cause you'll end up playing a lot of games in multiple Tamagotchis. Once you've got time, you can reduce their weight but only if you're willing to waste minutes of your precious life lol. In some other Tamagotchi versions, weight doesn't affect anything that much so you might as well just feed them snacks. For the P's, if you have an infrared USB, there's a game by Mr.Blinky that you can download that makes you win 200 G automatically without soing anything. It also lessens your pet's weight so I suggest downloading it if you have a USB.