the ones I'm thinking of are ones I've seen for sale in town - they're tougher and bigger than the beachballs you blow up, constructed like plastic footballs.

Like these, but huge. (http://www.southan.co.uk/8-coloured-plastic-football-5705-0.html)

I don't think I could stand there holding two dogs and inflate a ball from scratch, not with Spike going mental and Squish possibly terrified (he's not keen on large balls for some reason.)

I'm thinking I may need my mum to help me make this workable. She could walk Squish while I play with Spike. or something.