The Haro looks like a fine candidate for touring, especially if you're going to go on unpaved roads or rough surfaces.

THe first thing I'd check is whether it's possible to swap out the front fork for a rigid fork. Ask at the bike shop and consider the cost of making this swap. This is not essential and it might not be feasible, but it can't hurt to check.If you go this route, keep the suspension fork so you can swap back in the future.

Also, for touring you will find the wide knobby mountain bike tires are not your best choice. If you can go with narrower tires with more of a road tread, using the same wheels and rims, go for it. Again, have a good long talk with the people at your bike shop.

If you go with a trailer, I used a Burley trailer during a tour in summer and I was impressed. As another option, are you able to mount a rack on the bike? This would be my choice, especially for short and medium distance tours.