Play until Pikachu has Persian and Eevee has Nidoking/Rhyhorn

Pikachu:
Pallet - Pikachu
Forest - Caterpie (Evo x2), Weedle (Evo x2), Oddish
Route 3 - Sandshrew (Level), Mankey (Level), Magkarp
Mt. Moon - Clefairy (Evo), Paras, Geodude
Route 6 - Pidgey (Evo x1), Growlithe x5 (Evo 1), Abra (Evo x1), Jigglypuff (Evo)
Vermilion - Persian

Eevee:
Pallet - Eevee
Forest - Caterpie (Evo x2), Weedle (Evo x2), Pikachu (Evo), Bellsprout
Route 3 - Ekans (Level)
Mt. Moon - Clefairy, Paras (Evo), Geodude
Route 25 - Meowth
Route 6 - Vulpix, Abra, Jigglypuff
Route 10 - Rattata (Evo), Spearow (Evo), Nidoran F (Evo x2), Nidoran M (Evo x2)
Rock Tunnel - Rhyhorn

Trade ~1:10
Eevee - Bellsprout, Ekans (Evo), Meowth, Vulpix (Evo), Nidoking, Rhyhorn
Pikachu - Oddish, Sandshrew (Evo), Mankey (Evo), Clefable, Growlithe (Evo), Persian

Play until Pikachu has Dratini. Pikachu needs to blitz, so they shouldn't wait for any encounter until AFTER Dratini unless it is needed for EXP. Re-visit areas after Dratini is caught if needed

Pikachu:
Diglett's Cave - Diglett (Evo)
Route 11 - Drowzee (Level), Mr. Mime
Route 10 - Rattata (Evo), Spearow (Evo), Nidoran F (Evo x1), Nidoran M (Evo x1), Krabby
Rock Tunnel - Zubat (Evo), Machop, Cubone, Kangaskhan
Tower - Gastly (Evo)
Route 17 - Psyduck (Evo), Doduo, Ponyta, Eevee x3 (Evo x3)
Cerulean City - Bulbasaur (Level)
Route 10 - Dratini, Tentacool

Eevee:
Rock Tunnel - Zubat (Evo), Graveler, Machop (Evo), Cubone (Evo)
Tower - Gastly
Route 17 - Pidgey (Evo x2), Doduo (Evo), Ponyta (Evo), Psyduck
Route 6 - Goldeen (Evo)
Pewter - Old Amber
Route 21 - Staryu (Evo), Tentacool (Evo)
Cinnabar - Omanyte, Aerodactyl
Mansion - Koffing
Diglett's Cave - Diglett

Trade ~2:30
Pikachu - Bulbasaur (Evo x1, Level), Dratini (Evo x1, Level)

Play until Pikachu has all things that Eevee needs to Evo by Level up

Pikachu:
Power Plant - Magnemite x2 (Evo), Voltorb, Grimer, Electabuzz, Zapdos
Route 10 - Krabby necessary
Route 12 (just water) - Horsea
Cinnabar - Kabuto
Route 1 (or wherever) - Chain x11
Route 24 - Charmander
Seafoam - Squirtle, Seel, Slowpoke

Eevee:
Silph - Lapras
Saffron - Porygon
Dojo - Hitmonchan
Route 15 - Scyther, Venonat (Evo), Weepinbell
Route 23 - Poliwag (x2 if the trade happened already and evo one x2), Exeggcute
Victory Road - Onix, Moltres
Cerulean Cave - Mewtwo, Lickitung, Rhydon, Chansey, Magikarp (Evo), Ditto

Trade:
Pikachu - Literally everything that needs a level up evo (Voltorb, Grimer, Krabby, Horsea, Kabuto, Charmander, Squirtle, Seel, Slowpoke)
Eevee - Everything that needs a Level Up Evo as well

Pikachu:
Seafoam - Jynx, Shellder, Articuno
Route 15 - Gloom, Venonat, Scyther, Tauros
Route 6 - Goldeen
Dojo - Hitmonlee
Route 21 - Tangela, Staryu
Mansion - Magmar
Route 12 - Snorlax, Farfetch'd

Do the rest of the trades and evolutions with candies/stones that you picked up/bought. Trade the trade evos together (Machoke for Kadabra to sync move learn on evo as well)