What do they both love doing/watching? For DD10 would she like to choose something specific, or give you a list of ideas? I always get mine to do a list and stick to it, I've learnt in the past if I get random extra gifts they don't usually play with them unless they're closely related to what they asked for. Would it be a problem for DD8 to just get the one special present, if that's what she wants and knows not to expect more? My DD is also 8 and usually just focuses on one present so I fill in with things she needs like clothes that I was going to buy anyway (she loves getting new clothes, so it's not a hardship for her).