Models in base contact with the enemy can fight regardless of whether they are Squigs or Night Goblins. In the case of Squig Hoppers only the Squig fights, the rider is too busy hanging on to do anything else. Night Goblins are assumed to carry only basic weaponry as their armaments are really designed for herding not fighting - they therefore get no bonuses or special weapon rules, even if they carry spears, huge clubs, squigpipes or whatever.