Question: "Will it be possible for us to sin in Heaven?"
Answer: The Bible describes heaven in great detail in Revelation chapters 21-22. Nowhere in those chapters is the possibility of sin mentioned. There will be no more death, sorrow, crying, or pain (Revelation 21:4). The sinful are not in heaven, but in the lake of fire (Revelation 21:8). Nothing impure will ever enter heaven (Revelation 21:27). Outside of heaven are those who sin (Revelation 22:15). So, the answer is no, there will be no sin in heaven.
What does that mean for us? If there is no possibility of sin, does that mean we will no longer have a free will in heaven? Perhaps in heaven, our ability to choose will be similar to that of the angels. The angels had a one-time choice to obey God or follow Satan. There is no possibility of further angels sinning and joining Satan in his rebellion. The holy angels are "elect angels" (1 Timothy 5:21). Similarly, the elect in heaven will be "sealed" in their decision to forsake sin and trust in Christ. We will not even have the choice to sin. At the same time, having been delivered from sin and evil, and viewing the wonderful glories of heaven, we would not choose sin even if we had the choice.