Totally random, but Skin So Soft by avon will keep mosquitoes away. Also, if you're looking for a more natural method, mosquitoes are naturally repelled by marigolds. A friend of mine plants them in window boxes every year around their deck and it keeps mosquitoes at bay-no sweat! You could get a few, maybe pin one to your baby's diaper and stroller. As far as sunscreen, as I'm sure you know, babies are too little to have it on their skin. Most pediatricians recommend layers of light-weight, tightly woven (hold it up to the light, if none comes thru, it's a good choice) loose clothing to protect their skin. You may not have enough time to get it, but there are also clothes with UPF built into them (sun protection -usually like a 50 SPF). Just google UPF 50 and yo'll see what I'm talking about. Here's a link to just one website (recommended by the Cancer Assoc.) http://www.coolibar.com/childsunclothing.html
My kiddo was born in August, so I completely understand your dilemma. I invested in some of these clothes because I knew that we'd be on lots of outdoor activities before winter. He never got burned! I, (of course) tried to find shady areas, made him wear a hat, and kept him out of direct sunlight as much as possible as well!
Hope this helps, have fun!