Hiya Jason,
I love Laughlin. We've stayed at Harrah's, River Palms and Ramada Express. This spring we arrived in Laughlin the day after the biker event, (great time for getting River Run chips!!). So there shouldn't be any problem with the convention in June.
Harrah's has both smoking and non-smoking casinos and Laughlin's nicest beach area (but the river water is COLD). Harrah's dealers are among the friendliest you'll find anywhere.
If you like video poker, the River Palms is your place. Full-pay machines abound.
We usually stay at the Ramada Express. It's not riverfront but they have an adults-only hotel tower, a wonderful pool and they treat me well.
In June most of the hotels in Laughlin are relatively inexpensive. You could probably go to the Nevada tourist bureau website and get a link to Laughlin to find out what events are in town during June. No matter where you stay, get a slot card and use it. Then you won't have to worry about where you're staying the next time around because you'll very likely get discounted or comp rooms.