The thing with adventuring with low-level parties is that it can feel like the GM really has to bend the rules to make sure it's not just a TPK every time someone rolls initiative. Hamlet of Heroes looks to help, as it's a whole extended supplment of low-level adventures that your players can go on. The book is up on Kickstarter now.
From the campaign:
This supplement will include the Human, Elf, Dwarf, and Halfling races changed to reflect a less powerful world. It will also include the Barbarian, Cleric, Fighter, Paladin, Ranger, Rogue, Warlock, and Wizard classes completely overhauled to fit the new principles of their character designs. Spells will also be changed with many being ripped out with new mechanics surgically replacing the old ones, as well as several completely new spells that will give the feel the supplement is trying to instill.
These reworks include a higher frequency in players receiving skills through leveling, but a decreased health pool. This gives them more power, while keeping the scope of their adventures inside the realm of traditional "low-level" play. The players do gain strength however, and there are rules for how these new abilities effect the world around them. Rules for players taking on
The supplement also includes the mechanics for having different characters start at different levels at the beginning of a campaign, as well as race specific class options, ideas for campaigns that are low-level and enough ambiguous lore to feed a hungry world builder.
This book does require you have a 5th Edition Player's Handbook in some areas. It does not require the use of new monsters specially built for this supplement, so you can use all of those monster manuals you have accumulated over the years.
The Kickstarter is more than 2x funded, but with only 8 days left to go.