Sounds normal to me. I'd go in with him until he's adjusted. For my daughter, it was 10-15 minutes, but got shorter each time, until she acted like it was weird that I didn't just drop her off. It took about 5 months to get to that. My boys never really went through that.
I wouldn't encourage distracting him and then sneaking out. I've worked with kids in many different settings, and the parents who do that make it very hard on themselves, their children, and the workers. Your child needs to trust you. You can get him involved, but be sure he knows you're leaving. He's going to realize you snuck out on him otherwise, and then he won't trust you. With my daughter, I just waited until she had been having fun for a while, and then called her name and said I was going to go now and I'd see her later. She just said bye, if anything at all. If nothing else, know that this is a stage, and this, too, shall pass.