Get a pendulum sight for your bow, you wont need a rangefinder inside 30 yards if your shooting over 275 fps typically and you stay within 18 to 25 feet up in the tree once you get it dialed in.

Check your sight on your muzzeloader, in other words sight it in as close to using it as possible, wether that means a day before you go out or 2 weeks, just double check.