Rayvolution wrote "1:15min," which I read as 75 minutes.

Anyway, as long as both flights are on a single ticket, you're protected and the baggage is automatically transferred.

As CPH-Flyer wrote, you're arriving at one of the F gates (more specifically, F58, F59, F62, F65 or F69). After disembarkation, you'll take an elevator or escalator up to the fourth floor, which is a long corridor running along the length of the F pier. There should be airport strollers available there (I believe they are located at F58, F59, F65, and F66). You could take two strollers and use one of them as a baggage cart, maybe even the 5 year old would be willing to push that stroller.

After taking strollers, you continue until the end of the corridor, and take an elevator down to floor 2, where the passport control is. After passport control, go straight ahead to the security control (it's just 10 meters). After security, take an escalator or elevator up to the third floor, and that's where the gates are. If you're lucky, the flight leaves from gates F26-F39, which means a short walk. It's more likely that it leaves from gates 1-10. which means a medium long walk. It may also leave from gates 11-16, which means a long walk, but that's not so common.

There is one company doing porter service at Arlanda. They would normally only do porter service from the baggage claim belts to taxi/bus, but theoretically I believe that they could also help you with porter service for a transfer flight. They're called Bagport. They should be able to meet you in the corridor close to the plane and carry all cabin baggage for you. I have no idea how much this srvice would cost, though.