This may not work well because of the different soil pH requirements of these 2 plants. Blueberries are acid lovers (soil pH 4.0-5.5) & most grape info says they like slightly acid soil (pH 5.5-6.5). Your soil sounds like it might be good for the blueberries but need lime for the grapes but the only way to be sure is a soil test.

Wirosarian is correct that the blueberry pH is going to be lower than that of grapes for ideal performance from both.

I grow grapes in a clay soil with a native pH of 6.8 and have slowly tried to lower the pH just slightly with the use of acid forming fertilizers.

For my blueberries I removed the soil in a 2' wide by 1' deep area (per shrub) and back filled with 90% peat and 10% native soil and I scratch in a small amount of elemental sulfur annually so the surrounding soil can't raise the pH of the peat. (peat is naturally 4.something pH).

I think you probably could grow both grapes and blueberries in the same soil (shoot for a 5.5 pH), but I don't know that either would be getting the 'optimal' conditions, kind of a compromise solution.

If you attempted to lower the soil pH lower than 5.0 for anything other than the blueberries you might run into an aluminum toxicity issue. Personally I advise to prepare each soil separately.

You'll need lots of space for this to work too. In addition to the different pH requirements, blueberries have a very shallow root system and don't do well with competing roots. Grapes have very large root systems to support their vines.