We are traveling to Spain in March arriving in Barcelona on a Sunday morning and leaving Madrid a week later on Monday, so 8 days. This is the first time in Spain for our family of 3 (teen son). Would it be too much to include Seville and Toledo in our itinerary? Any suggestions on how to divide up the trip? Thanks!

Toledo would be fine
Seville not so easy
Girona & Figueres both very possible

All depends on what you want to see and to do. A somewhat serious visit of Barcelona, Madrid or Sevilla needs AT LEAST 3 FULL DAYS for each city, more if you visit the surroundings.
If you arrive at BCN Sunday morning after a overnight flight, you may not be able to do a lot Monday, all somewhat important museums will be closed. There remiains a lot to do nevertheless.
But it will not be possible to visit all of the most important museums in one single Tuesday. You may therefore add Wednesday morning and move immediately after lunch, may be with the 16.25 train, to Madrid ar 18.55.
You will then have 3 days for Madrid and one full day for Toledo.

IMO, yes.
Barcelona itself easily merits 6 full days.
Madrid along easily merits 4 full days.
Sevilla easily mertis 4 full days.
Many people visit Toledo as a day trip from Madrid; I thoiught it worth 2 full days.

I think you would do well to consult a decent guidebook.

In Barcelona and Madrid there is a great deal to see and do without spending hours in museums .
If there is a particular interest in a period , or an artist one can focus on those.
Both cities have great parks, interesting architecture, lovely avenues, markets ,etc
Barcelona has a lively waterfront, Madrid , as imposing Palace.
Toledo is an easy day trip…but , again one cannot visit all the attractions..just select a few.
Seville would be very difficult to fit in your itinerary.

I'd keep it to just the two cities, maybe taking a day trip from Madrid to Toledo. You really don't have time for Sevilla.

Thanks everyone! We will be spending 4 nights in Barcelona and 4 in Madrid. Any suggestions on best areas in each city to get an airbnb or hotel?

Sounds good. The accommodation may depend on your budget. If you search the Forum, you will find helpful information from the locals : Maribel and Revulgo, and ,of course ,
numerous posters.

Centrally located hotels
https://www.google.com/maps/d/viewer...609751456&z=15

Thank you for that fantastic map!!!!

We did a similar week-long trip when our daughter was a teen. We did aside trip to Girona and Figueras from Barcelona. We flew to Madrid and did a day trip by train to Toledo. Loved Barcelona.

Seville we saved for a separate trip to Andalusia, including Grenada and Cordoba. Loved Seville.

Thanks everyone!