Many tournaments are held at hotels on industrial carpet. I would think it totally ok, especially at home amongst friends and family... Narrower feet are likely better as they will compress the footprint better; you might have to let the table settle-in for some time and then level the table-playfield. If your carpet is really mushy...well you might have minor wandering issues with light jarring, leaning, and heated play.
The only drawback I can guess at would be if the kids figure they can lean on the rods to control ball. Their small degree of ball control will vary depending on the pile / underlay thickness as well as pressure applied; but when used skillfully can tip a close game and/or lead to arguements... I would expose the trick quickly with your kids and remove it from their foosball vocabulary.