Parc Guell to Sagrada Familia

We did Park Guell with a first of the day ticket and scheduled La Sagrada Familia at 3, mostly because that was the time I could get. Ideally, a 2 time slot would have been better, but we did fine. It is an easy bus ride between the two sites. I think given July hear, your plan is a good one. Perhaps 3 is a good choice and you can stop somewhere inside for a cool drink or a meal in between.

Did you stop to eat somewhere in between?

This isn't what you asked, so apologies. Can you do them on different days, two successive mornings?

In short: PG in early AM and SF right after (our) lunchtime, with a walk thru bohemian Gràcia. Then, afterwards, you have time for a third visit, to Sant Pau Centre Modernista (previously referred to as Nou Hospital de Sant Pau). On your way there, a short 15' walk from SF, stop by Mora patisserie, in Avinguda Gaudí 60, and purchase some "catànies" -worthwhile!

For details: check WED16 on this thread: http://www.tripadvisor.com/ShowTopic-g187497-i44-k7350676-First_Timers_Help_With_5_Day_Itinerary-Barcelona_Catalonia.html#57433425 and this is the map it refers to http://bit.ly/DIYroute-pg-sf

And for some background on the history of the park: https://community.ricksteves.com/travel-forum/spain/barcelona-palau-guell-or-park-guell

Jessica - due to limited time, we are going to have to see both places in the same day.

Afternoon tours at SG are either 1:00 or 3:00. No 2:00 exists on the day we want to go.

I did see one post from 10 or so years ago where the person went to SG in the morning and the Parc Guell at 6:00. Not sure how to fill up the time if we spread it out that far.

Hospital de la Santa Creu i Sant Pau is a great way to burn a couple of hours between Sagrada Familia and Parc Guell. The hospital is a couple of blocks uphill (easy walking distance) from Sagrada Familia and is well worth seeing.

There are plenty of restaurants along the shady road between Sagrada Familia and Hospital de la Santa Creu i Sant Pau, so you could grab a bite there before heading up to Parc Guell.

Be warned that a good chunk of Hospital de la Santa Creu i Sant Pau's sights are also outdoors, so it might not help you avoid the heat much. But the hospital itself is very worthwhile.

We did Parc Guell in the morning and then Sagrada Familia in the afternoon. (because of the heat issues and this was in October) Because of the heat issues in July, I think that's the right plan.
First, we were staying near Placa Catalunya, so getting to Parc Guell was convenient. we took the #24 bus from Placa Catalunya that went up the Passig de Gracia then up the steep hill and stopped at the back entrance of Parc Guell. The walk from the bus stop to the back entrance was about 50 feet. This back entrance was also where the guided tours start, so it was perfect for us.
We booked a 10:00 am English guided tour of the monumental area. So we caught the #24 bus at 9:00 and were there by 9:40 or so.
The guided tour gets you immediate entry with your guide and was worth the cost. The tour is about an hour. and ends inside the monumental area, so you can stay inside that area for as long as you want. After we left the monumental area, we walked around the park, then walked up to the cross, before following the trail to the exit on the South West side. We had lunch at the top of the stairs/escalators at Guelly sandwich park around noon, before walking DOWNHILL to the metro station. (you do NOT want to do this in reverse- even with the escalators - uphill). We walked to the Vallcarca Metro station, made one transfer and got off at the Sagrada Familia Metro station. And when you get out of the station, Sagrada Familia is right there!.
We booked an English Guided tour at 3 pm, with a 230 pm entry so we had some waiting time outside the paid area, and in the gift shop, and in the park across the street. You could possibly book a 1 pm tour, but I think you'd feel rushed. You can also do you own audio tour at other times. The guided tour was worth it. We did not climb the towers.
If you just want the audio tour and not the guided tour, I think a 2:00 pm entry time is reasonable. A 230 pm entry was almost too much waiting time.
With timed tickets, SG is not over-crowded. Only so many people get in at a time.
I think Parc Guell in the AM, and SG in the afternoon is a wonderful, reasonable plan. Enjoy!

We ate a quick lunch while we waited for the bus to la Sagrada Familia. When we got close to La Sagrada we stopped first for churros and chocolate (in was January) and then walked around the little park that has great views over the lake. We lingered a lot at Parc Guell, we loved it. BTW, there is a really nice museum in the basement of La Sagrada Familia. See it if you can.

Another vote for the Parc first- we did this in July a few years ago. We were there before opening and it was very warm already. You get the lovely view out over the city. We didn't use a tour. Then as others said we started to make our way back gor the 3:00 Sagrida time. The hospital is really interesting and your kids will enjoy the ghostly figures, operating theatre, etc- plus I remember it being cool in the tunnels! For sure go there!
We actually fit a couple of the most famous houses in, too, before 3 but I wouldn't try that with kids.
The church was more of a stand in awe and slowly wander type of experience, since by then you will be tired.
Have a fantastic time!

Tickets for Parc Guell now include a shuttle bus ticket, but I'm afraid I don't know where the pick-up/drop-off point is.

@acraven:
Plaça Alfons X el Sabi, close to the Alfons X metro station (line 4, yellow): https://www.tmb.cat/en/barcelona/metro/-/lineametro/estacion/429

For info:
"X" is 10th in Roman numerals, not the letter "x". Sayin' so because it's very funny sometimes hear some of our friends from English speaking countries asking for "metro alfons ecs", LOL!.... it should be, in Catalan, the local language, "metro alfons deh-ow", thus any local should know what you mean.