What types of bikes are you looking to put on there? If you’re talking two adult bikes and two kid bikes, the Yakima or Allan arm extending ones work fine. It’s definitely a tight fit with all four, but very doable. Dropping the level to access the hitch though with four bikes is a bit tedious. The end bike tends to lay the tires on the ground and it’s just cumbersome. If your kids have larger bikes, it’s nearly an impossible fit to get 4 on an arm rack.
Kuat swing rack is definitely what I’d go for if you’re willing to spend 1,500 or so. They make everything so much easier and also are steady.
If you do end up with an arm rack, I’d also purchase a clamp that prevents side to side swag. I’ll see if I can find the one we use.