Sweaty baby

Anyone have tips for keeping baby cool when out and about? My LO gets sooooo sweaty and hot in his car seat and we're planning an outing this weekend. I've got a stroller fan on order and I have a cooling liner for his car seat that does nothing. I've thought of bringing our Bob stroller and just laying the back down so it's angled up slightly, that way he's not stuck in his car seat the whole time. He's a really big baby so i think if he has more room he'll be more comfortable.any tips are appreciated!