What size table?
I always take a couple of deathstrikes for laughs. They make their points back just don't waste them against holofields.
I've been playing Siegemasters a lot so i'd say bunkers and artillary. You have the rt at least!
Manticore batteries are nice addittions, don't be afraid to alpha strike for the added Bm if you reckon you will break a target. However I love using them against fleeing eldar (as BM don't stick with them turn for turn unfortuently). Basilisks are also neat against elder, if only for that very long ranged direct fire ability. I don't know if I would field a company - maybe!
Hydras are a must everywhere as is having a supreme commander.
Flyers at 5000 points get chewed up unless they are very good so flak is a better option. A squadron of thunderbolts is compulsory for me though (no tactical reason I just like them) and could be a laugh.
Infantry garrisons on objectives form speedbumps.
As its eldar I'd also do cheesy stuff like giving the Leman russ ogryns in chimera. Oh and vultures are good for turn one AT burst of firepower.
Essentially if you are outclassed try and out firepower him, hopefully with stuff that ignores clevel clogs eldar hiding techniques.
Overall though I'd take my siege army and see if he has enough shuriken
