This could be super simple...and I really don't see any reason to limit it to 2 of the racial features...they all have more than that. Include sub-races into the mix and you can have a whole smorgasboard...but we'll keep it simple for now.

I'd go something like this:

"If you want to be a race other than human, you can spend some of your ability score bonuses to purchase racial features to flavor your character as a certain race. Select one of the Races below to select different traits. Bonuses spent on racial traits can not exceed 4 of your 6 initial ability bonuses. All features must be chosen from the same race. Once chosen, these features can not be changed but additional features, within your set race, may be purchased as your character's Ability Scores increase."

Dwarf
Twilight Vision: Cost 1. You see can see in low-light conditions, discerning color and detail, to a distance of 60'.
Stonecraft: Cost 1. Add your level to ability[skill] rolls to notice or examine stonework construction, traps, secret doors, shifting walls, etc...Also, you always know which direction you are going when underground.
Dwarven Constitution: Cost 1. Add 1 + double your Constitution bonus to save rolls against poison or disease.
Weapon Expertise: Cost 1. You are +1 to hit with axes and hammers.
Dwarf Languages: Cost 1. You know the following languages in addition to Common and Dwarven: Orc, Goblin, Kobold, Giant, Gnome.

Stoutfolk Resistance: Cost 2. Add your Constitution bonus to save rolls against spells and magic effects. If the normal spell save uses Constitution, then your modifier should be doubled.
Darkvision: Cost 2. You see in natural darkness as if it were low-light and low-light as if it were full light to a distance of 60'.
Ancestral Enmity, Orcs & Goblins: Cost 2. Gain +2 to damage when you hit Orcs & Goblins.
Ancestral Enmity, Giants: Cost 2. Gain +2 to your AC due to your small size when fighting giants, ogres or trolls.

Elf
Twilight Vision: Cost 1. You see can see in low-light conditions, discerning color and detail, to a distance of 60'.
Elfin Agility: Cost 1. Add 1 + double your Dexterity bonus to rolls to dodge, balance, or climb.
Keen Senses: Cost 1. Add your proficiency bonus to Perception rolls.
Weapon Expertise: Cost 1. You are +1 to hit with long or short bows and long or short swords.
Elf Languages: Cost 1. You know the following languages in addition to Common and Elvin: Orc, Goblin, Gnoll, Sylvan, Gnome

Elf Magic: Cost 2. Select 1 cantrip from the Wizard or Druid spell lists that you know. At 3rd level select another cantrip and one 1st level spell from the Wizard or Druid lists. At 5th level you add a third cantrip and second 1st level spell. You cast the cantrips at will, as normal. The spells you can cast once per day. Intelligence is you spell casting ability for using these magics.
Faer Folk Heritage: Cost 2. Add double your Intelligence bonus to save rolls against charm spells and magic effects. Also, you can not be put to sleep by magic and are immune to the paralyzing touch of ghouls.
Darkvision: Cost 2. You see in natural darkness as if it were low-light and low-light as if it were full light to a distance of 60'.
Woodstealth: Cost 2. Add your level to ability[skill] rolls to hide and move silently in forests and other natural surroundings that are not underground. You always know what direction you are going as long as you can see the sky.

Halfling
Easily Missed: Cost 1. You are +4 to your AC against foes who are larger than human-sized.
Halfling Hiding: Cost 1. Add your level to ability[skill] rolls to hide or move silently anywhere.
Brave at Heart: Cost 1. You have advantage on saves against being frightened.
Stoutfolk Constitution: Cost 1. Add 1 + double your Constitution bonus to save against poison and disease.
Halfling Languages: Cost 1. You know the following languages in addition to Common and Halfling: Orc, Goblin, Elfin, Dwarven, Gnome

Luck o' the Smallfolk: Cost 2. When you roll a 1 on a d20, you can roll again. You must use the second roll.
Hairfoot Charm: Cost 2. Add 1 + double your Charisma bonus to interactions with a creature whose language you can speak.
Weapon Expertise: Cost 2. You are +1 to hit with slings or short bows and daggers or short swords.
Stoutfolk Resistance: Cost 2. Add your Constitution bonus to save rolls against spells and magic effects. If the normal spell save uses Constitution, then your modifier should be doubled..

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