An IRL3103 should work. The RDSon
increases to about 0.016V at 4.5V VGS
(close to typical at an MCU output). That would mean about a watt of dissipation at 7.6 amps. Given a typical TO220 I think it will get to about 60 degrees above surroundings at your maximum. Okay for the FET, but you won't want to touch it or keep it cooped up.
I use little heatsinks when I push TO220 devices to a watt or so. Kind of like these: http://www.aztecmcu.com/catalog/i99.html
They still get warm, but not so hot they could burn you or melt something.