If you are, ahem, less than svelte, being pg in summer has advantages. You can wear whatever you want and no one can say anything at all. If only it were always the case.
Both mine are summer babies (July and late August) and what I have really really hated is being fat during the summer after the birth.
Another downside is that you are in 1st trimester Xmas so can't drink (much) but can't say why, and may be feeling lousy.
The school thing is a worry, to the extent that we will probably send them to a kindergarten. But I am REALLY against anything that looks even slightly like academic pressure, so I would not send a just-4 year old to school. (I don't even like the idea of nursery schools-round here they seem very academic). Dh thinks differently but accepts that I am in charge.