Connie, Yes, if you can get to Tikal, go! But... don't do it from the island, if that possibility actually still exists (because flights to Flores from Belize are no longer available with Maya/Tropic).
When I did it in 2005, I was able to fly from Belize City to Flores and took a taxi to the park. Once there I found a guide to give me an informal "night walk" through the trails surrounding the little hotels on site. Then I signed up for the sunrise tour, which was amazing. You have get up at about 4am to do it, but it's well worth it. Afterward, I talked to the guide again about seeing other sites in the area. One I was particularly interested in was Yaxha, which is where they had filed Survivor, Guatemala that year. It's possible to do organized tours from the area, but I remember they cost between $150-200+. The guide called one of his friends (an off duty guide) and arranged for him to take me to the site for my own private little tour, for only $80US. Those few days were one of the highlights of my trip.