Friends just did a spring trip to AK and said they had every type of RV in the caravan (20 RV's)there is from truck campers to class A coaches. Not sure why you think the Itasca won't handle it. It is your decision. Our friends have a 5er and said the roads are rough so make sure you batten everything down really well. There were lots of stories of what messes had to be cleaned up after every move, from the fridge coming open and actually tilting out of its opening to cabinets coming open to furniture dancing all over the trailer.
We travel with our cats too but we can let them wander about the truck with no problem. The litter box issue we solved by using a clear plastic bin and cutting a hole in one end and put a small litter box in it so it contains any "misses". Works really well BUT, if they should heed the call of nature you WILL be stopping to dispose of it as soon as you are able. Trust me, I know. Keep a scooper and some plastic grocery bags handy to put it in. Have a great time on your trip.
