Recreational & Family - mountain to hybrid?

Hello,
I ride an '88 Trek 820. I pull my two daughters in a trailer with it. We do primarily road and packed trail riding. I was told by the guy at the bike shop that I need new tires. I am looking for suggestions on what type of tire to get. I do not want slicks, as I need to option to ride on trails and suck. I also do not think I need big, fat, knobby tires either, and they slow me down quite a bit. What would you recommend? What brand? Could a person convert a MTN bike to a hybrid type by changing to thinner rims and tires? Thanks for any response.
Pat

The Specialized Hemisphere tires are a 26 x 1.95 tire and aren't real aggressive but at the same time are pretty wide. The Nimbus is also available in a 26 inch at 1.5" wide, but they are really designed to be a strictly pavement tire. I'm sure that there will be some other recommendations, these are just what I am familiar with and they are reasonably priced.

I've got a new Trek 3900 and had my LBS switch the knobbies with Bontraeger Inverted street tires with Kevlar. They cost about $19 each but are very quite and tough. I ride mostly road and bike trails as well yet there is still enough tread to do some light off roading with these tires. I kept the 2.00 width but could have dropped to 1.50 with the stock rims. Hope this helps.

Mark

If you're riding on dry dirt, you would be surprised how well 1-1.5 in "slicks" work.

Thanks for all the advice. I appreciate it. I have looked on the net a little and noticed the Michelin Sprint 2 tires. Does anyone have experience with those? Also, I have had Specialized Fat Boys in the past, and were great on the road but not so great when it rained. In my initial post, the word suck was supposed to be such! They did not "suck". :) Any more comments are appreciated. The Bontrager Kevlar inverted's look like something that may be ideal for me. Thanks again.
Pat