Chalk paint is very easy to use. I would get higher quality than Home Depot. I tried some I purchased from there and didnt really like it. In fact I painted my floors am doing them over again right now with a higher quality chalk paint. I recently painted a bathroom vanity using Renaissance chalk paint from Amazon and I really liked it. It is a very easy process as there is no sanding or priming required prior to applying the paint. You are supposed to use wax after the paint dries. My guess is it will cost you about $100 for paint and supplies needed for that many chairs. If labor is free then you will be well below your $500 budget. Enough money to throw a dinner party for 10 special guests after all the paint dries to show off your new chairs.

https://www.amazon.com/Renaissance-Chalk-Furniture-Cabinet-Paint/dp/B00S517T14/ref=sr_1_1_sspa?ie=UTF8&qid=1510094209&sr=8-1-spons&keywords=renaissance+chalk+paint&psc=1

What does your table look like? My first thought is to do them in black...

yes, chalk paint is easy. clean those well w/tsp and make sure you rinse well. I like to sand (even tho you don't have to) to remove any rough spots. paint two coats, lightly sand, then wax and buff. chairs are a lot of work to paint. I usually spray them. but try a few w/the chalk paint and see how you like it. I haven't used HD brand, but have used all the other big names. I usually make my own. (Behr sample pot paint and plaster of paris powder. 2:1 ratio, hot water)

try a nice charcoal gray or the black.

I have no advice, but would like to offer a fabric for curtains or other, if that'd make a blend.... Best wishes!!

Oh, the long shot is that you might like current chairs, mixed together! ... or this fabric with yellow chairs, and paint the others the background color:

hey, a nice pink chair would look great w/that fabric!

so here's a chalk paint chair. plenty of examples online, and plenty of videos. here is one of them:

https://www.youtube.com/watch?v=DyD_jfLvc8M

Luckily, they don't have rush seats so painting will be more straight forward, BUT that high gloss finish will have to be taken off for a paint job to work. If we could see your table, we'd make more valid suggestions. I tend to lean toward coordinating them with fabric and textiles in your room and leaving them the color they are - much easier solution. Spend your $500 on that.

just as a suggestion,,,I see these round oak table all the time on Craigslist for super cheap. (I actually picked up one for $10 and refinished it to look like this:

btw, if you could do another bench seating on the window behind the table, your kids could have more room to sit and do their work!

you could get a stencil and do this to your existing table w/chalk paint. (make sure it's on the dry side and go lightly) and then coat w/a few coats of poly

for bench cushions, since that's a custom size, try Etsy or maybe pier one would have one that would fit.

curious,,,,you didn't want a small overhang on the island so you could put a few stools there?

Especially if table will be mid-toned wood, blue chairs add youthful interest. It doesnt have to look sloppy if rest of chairs match something - probably white of cabinets. Personally, i like the look.