At $11-$13 and , Neutrogena's Wet Skin Kids Sunblock spray is a bit pricier than some sunblock lotions--but it is also amazing.
At first I was a naysayer--when my cousin whipped it out by our pool, I thought "what is the point of this fancy-shmancy stuff?" The point is that you can spray non-cooperative tikes with the stuff in just a minute or two (no more rubbing and rubbing in lotion) and. most importantly, it really prevents sunburn! I even spray it in Andrew's hair--what an improvement over lubing his head with lotion.
Wet Skin Kids SPF 70 spray applies on wet or dry skin, is water-proof and sweat-proof, and is oil free (no slippery babies). And I think it smells pretty darn good! (I even use some myself--they do make an SPF 85 that can be used on kids 6+ months too.) Sometimes the spray can shock an unsuspecting kid, though, so you may need to proceed gently, especially on the back of the neck.
Be safe in the sun and enjoy the weekend!