If you can ride 50 now unloaded.. You can ride 50 miles loaded. It's just going to take you quite a bit longer if you have hills and or wind to deal with. You have at least 14 hours of daylight. Start early and break often. Suggest something like 10 miles between breaks. Make them longer than a few minutes. Eat and drink before you're hungry. Repeat.

Also.... You will soon find out