I would drop the day-trip idea... exhausting & too much time back/forth.
DAY ONE - Since u r from Vancouver, you will be tired on arrival ... exhausting trip. What time of day, exactly -- this is VERY Important when yr trip so cruelly short.. every minute matters. I would suggest if you come in in afternoon, stay near airport in place with free shuttle to/from (Either Hotel Avra or budget hotel PEris). Either one near to pizza place and beach, & u can conk out early to recover).
DAY TWO thru ? FIVE? Next AM, pick up car Rental at airport and head for 3 days in NAFPLIO -- and a Great Adventure for active teens w. interest in Ancient history/mythology! FAb Map shows all from Airport to Peloponnese - https://tinyurl.com/zekuft9 - (click & it gets huuuge, navigate w side-slides)
- ARGOLID/NAFPLIO Siteseeing options:
• CORINTH CANAL - jump off big road @ Isthmus, walk over Old Bridge, take pix, back on highway (30 mins)
• ANCIENT NEMEA - "Olympic Runner-Up" Sacred Games Site, just 5 mi to yr right off highway -- temple ruins, FAB stadium, kids can race from starting-blocks 2,500 years old (!!) ... NO crowds.
• NAFPLIO -- The BEST website = http://www.visitnafplio.com/ -- read EVERY link (FOod, hikes, beaches, ruins etc)
Considered THE most beautiful Old TOwn in All of Greece... but also super-fun time for Kids (castles, forts, adventure). Since u are planning faar ahead, u can book THE best-located place in town, HOTEL AGAMEMMNON...triple room w sea-front balcony, lovely buffet breakfast, AND Moderate price. A few of your adventures -
(1) Acronafplia & Park peak, (2) Bourtzoi Castle (3) sealevel walk around Point (4) PALAMIDI !! (tip: dont walk up; taxi up back way & walk DOWN 999 steps) (4) TIRYNS fortress (just outside town - NO crowds, more fun for kids than mycenae)
(5) EPIDAURUS -- after Breakfast on Day 4? - drive EAST (see map) to ANCIENT EPIDAURUS... mainly the Amazing Theatre, have kids climb to top, YOU whisper from stage... then drive to seafront & up the shoreline to Isthmus & re-join Big Road back to AIrport.
ATHENS - 2? Days -- Acropolis & Acropolis Museum -- USe R Steves FREE download podcasts on phones foro D-I-Y walk on Acropoolis... Acropolis museum also has audio guides. If u try Nat. Archeology Museum, R Steves again has FREE Audioo-guide of "10 Top Must-Sees" .. u can download, review in advance, decide if your 2 would like that.
ONE DAY LEFT??-- Then I do allow One DAY TRIP ... to AEGINA -- http://www.greekisland.co.uk/aegina/aegina.htm ,,, this gives you a genuine ferry experience (only take conventional open-deck ferry, NOT closed-cabin hydrofoil). Video shows possiblities... also Metro to/fromo Piraaus. Check weather forecast so you'll have a sunny island day as a finale!
DELPHI? - 3 to 3 1/2 hours drive each way, & hard to comprehend for that age, even mythology lovers... save it for future...