Is there a practical way to make belgian fries for four at home?
I would definitely not try this in a frying pan. Deep frying a lot of food can be dangerous, because if the oil overflows, it's flammable. I'm sure you've heard the horror stories of people deep-frying turkeys and the oil overflowing.

The minimal set up you will need is a large, heavy bottomed pot, preferably stainless steel or cast iron, though heavy gauge aluminum is cheaper and would probably work. You want the pot to be large enough to accommodate the oil, plus a lot of extra space because the large amount of fries are going to displace a lot of oil. To maintain the proper temperature, you'll need a good deep-fry/candy thermometer. Digital thermometers are a bit more expensive, but are easier to read. I'd recommend getting one that clips onto the pot. You're also may want a basket, because pulling them out with a spider or strainer will take a while and could lead to uneven cooking. You will need to monitor the temperature and adjust the heat on your stove regularly in order to maintain the proper temperature. You can get a stovetop fryer with a basket for under $30. 

A professional fryer uses a thermostat to control the temperature more precisely, and is built specifically for this purpose, so it's pretty safe. Generally these are electric, so they're inexpensive to run. But the issue for you is, they may not accommodate enough food. You might consider getting two, though the good ones run around $80-100, and depending on the power needs you might need separate outlets/circuits to plug them into.

Lastly, if you have outdoor space, you might consider doing this outside. You can get yourself a turkey frying kit at a hardware store or online. This will work well since it should come with a basket. You can also buy a propane burner and pot separately, if you need a special size or what a heavier pot. You'll still need to use the deep frying thermometer. A propane burner will have a control knob to let you adjust the heat and keep it at the proper temperature. This is probably going to be the fastest method for you to heat up the oil, as propane burners put out a lot of heat (often 100-200,000 BTUs). As always, you'll need to observe the proper safety precautions, like keeping a fire extinguisher nearby, and making sure you don't have too much oil in there to avoid an overflow, etc. The burner can also be used for other purposes, such as cooking with a wok, or frying/boiling other big items. A lot of people also use them for homebrewing beer.

Lastly, you should check this video out - it goes through the process they use to prepare authentic fries at Pomme Frites, some of the best Belgian fries in NYC - and according to their chef who trained in Belgium - they're better than a lot of what you'll get over there!