Mexico itinerary advice?

Hi all, want to do cancun (chichen itza, isla mujeres, possibly a tulum day trip) and was thinking 7 to 10 days trip is it worth combining with mexico city as well? (Slightly put off by flight in middle of a trip in case it feels too much travelling and just from reading online that mexico city might get upset stomach?) Any advice appreciated! I'm not sure if will necessarily go to mexico again or anytime soon after this so wanting to make the most of it but also don't want the trip to end up exhausting either. (Have done flights within country before eg cappadocia and Istanbul and found it ok though). Or if any other suggestions apart from mexico city to combine with cancun? Another reason for cancun is that there are direct flights there so just less hassle to get to. If just do cancun with the day trips would be 7 days and if combine with mexico city would be 10. Thanks!