K.H.
I had a similar situation (my ds was 13 months when my twins were born) I also didn't opt for a triplet stroller as my minivan can only hold the double stroller ended up with. I have to keep the back seat up b.c I also have a grade schooler who needs to sit back there. We went with the graco double stroller (i had an single evenflo for my 2 yr old and was not impressed with the quality) and we've loved it. They are rather bulky but it would be hard to find any double stroller that isn't. Its definatly not high end but we didn't have unlimited amount of money to spend on one either. I wouldn't recommend the side by sides as I would think you would run into plenty of situations where it would be too wide to get through iasles, doorways etc. Contacting her local multiples club about this question would be a good idea, she'd be able to get a lot of good feedback there.
K. H