Hello team, I need your help and suggestions
We've got a trip planned to Costa Rica and I've now learned that I can stay another 5 days.
We didn't get cancellation insurance. The cancellation fee is $250 and booking another one way ticket there is $250. It's still in our budget.
If we add the 5 days to the start of the trip, book a separate ticket there and ignore the original booking they will automatically cancel the return flight = this is a bad idea.
Here is the question, what if we don't cancel the original return flight, we buy another returning ticket and just ignore the one that was already booked. Will this be the most affordable option?
Advice would be appreciated.

You have to fly the first stage of your original flight or else that whole itinerary will be cancelled, so go to CR on your original flight then just drop your return portion (just don't show up at airport), extend your stay by 5 days at the end, fly home on your new one way ticket from CR to YVR. We have done this a couple times with no problem (Key is that you can change the end of the trip but not the beginning without major consequences)

Excellent, I was hoping it was a good option. Thanks.

is this with a voucher/\?

No, not using a voucher.

If you are flying United, ZERO flexibility!

You're cancelling the return so you can be as flexible as you want in it no matter the airline.

If you're willing to pay the extra fees, why not just call the airline, modify the return date, and extend your hotel?

I'll have to call and find out.

Did u ask about the change fee to extend your return? No option for that???

Once you arrive at destination, politely ask about changing return date. Not likely, but worth a try!

Talk to the airline. These things happen all the time, and they can advise you best.

Paulette I made several calls, and you were right, just not showing up for the return flight and booking another single flight is the best idea.
Changing the return flight would cost us either $417 from SJO or $684.63 from LIR per person.
google flights shows that one way flights booked through westjet today start at $302 taxes in PP.
If I use my aeroplan miles it's only 39,000 miles and $151 PP.
I hope this helps other people.
Thank you everyone for the help!
P.S. no one can help me change the car rental dates. Because I used aeroplan miles, they wanted me loose the original booking and pay for another one. I even called Avis. I'm just going to see if I can renegotiate when I'm there (I speak Spanish). Otherwise we'll make a day of it when we have to rent another car, and pick up more culture from the capital city.