Hello Shalmi!
Welcome to
planDisney my friend! I'm excited to see you here and am glad that you are planning on how best to enjoy the Parks with your little one.
I have two kids right around your son's age and the only place we use strollers is Walt Disney World Resort. A day in the Parks can be long and tiring for even the most energetic of kids. On my last trip, I found that I had walked 10,000 steps by 10 AM! Walt Disney World Resort does have strollers to rent in each of its parks. The single stroller is recommended for children 50 lbs (approximately 23 kg) or less while the double stroller is recommended for children 100 lbs (approximately 45 kg) or less. Since you stated your song is 40 kg (approximately 88 lbs) then I suggest you rent the double stroller. Prices are subject to change but the double stroller has a daily rental of $31 and a Multi-Day (Length of Stay) rental fee of $27 per day. I looked up my receipt from my last trip and found that the price per day included tax. For example, I rented a single stroller for 5 days which is $13 per day and it totaled $65. The "Multi-day" rental price is the best deal and what I suggest if you are visiting for several days. It was one of the best investments for our trip as my kids struggled with all the walking and needed a place to rest while I still wanted to keep moving.
When you enter the Park just head to the Stroller Rental location which is near the entrance. If you choose to purchase a "Length of Stay" or "Multi-Day" rental then you will pay once on the first Park day and then get a receipt which you must keep in a safe place. You will be given a stroller that you can use for your day but must return before you leave the Park. The next day you visit any Park, head to the stroller rental location, and show your receipt and Cast Members will stamp it with the date. You will not have to wait in the cash register line but head straight to the Cast Members manning the stroller area. It should only take a few minutes and you are then off with your stroller and ready to enjoy your day!
The only negative with renting directly through Walt Disney World Resort is that the stroller cannot leave with you as you leave the Parks. Your little one will have to find the energy to walk to the transportation area. Have a motivating speech ready and snacks to get them to where you need them to be. I know that this is what I have to do. If you wish to rent from an outside vendor, you can keep the stroller with you for the whole trip. Disney's Featured Provider is ScooterBug but I did review their inventory and found nothing that could fit one child that is the weight of your child. There is a double stroller that has a 100 lb capacity but it has sectioned seating which means it's truly intended for two kids and would be a bit tight for your child to fit in. However, the strollers you rent from Walt Disney World Resort have bench seating which means your son will have space to relax and maybe hold a bag or two next to him. (Great for all of your shopping that you may do.)
I hope this helps and if you have any questions please feel free to
let me know.
Happy Planning!
-Nimmy