It's never bad to have a couple of control spells. Just the classics like web and grease. If you're worried about provided the best tactical support, I've never seen anyone go wrong with summons. Ask your GM first if he'll allow summons though.
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Off the top of head though, I'd use your crossblood to have one blasty bloodline and one supportive bloodline. Something like Elemental/Arcane for example.
Remember that spontaneous casters can swap out an old spell for a new one (when raising a level), which is pretty good for spells that are only effective at low level like sleep or a save 'that evades all effects' spell.
Considering the size of the group, playing a bard would be pretty effective as well. But make sure to play what you want and have fun.
are you asking for advice on building a sorcerer, or advice on building your party's first 'true caster'?
if you just want to make a sorc:
personally, i think crossblooded is a trap... -2 to Will saves (and no real need to prioritize Wis) leaves you with basically 0 good saves, and losing 1 spell known/spell level means that even though you gain new spell levels every even level you'll know 0 spells of that level until you level again (so, at 6th level, for example, you gain 3 third level spells/day but you know 0 3rd level spells so you can't actually cast a 3rd level spells until you learn one at 7th... unless you take a metamagic feat just to make 1st or 2nd level spells into 3rd level spells, but then they'll take a full round action to cast). you're better off spending feats for the Eldritch Heritage line if you want powers from 2 bloodlines. crossblooded is really only good (IMHO) for dipping if you're optimizing a blaster wizard (the arcana benefits from 1 level of elemental/draconic sorcerer can be a pretty big boost for an evocation wizard).
i'd suggest choosing one bloodline that supports the kind of caster you want to be and jusr running with it. sorc is easier to use than wiz because you only need to really understand/remember the spells you know instead of everything in your spellbook, and you don't need to worry about preparing spells each day. the flipside of that coin is that your selection of spells known is very important... don't overload on any one type of spells- go for a mix of blasts, utility, buffs, and control. and when you see a spell that you feel like you really want to have "just in case" but know you won't use very often at all, remember that you can buy scrolls for just such occasions.
if you're interested in other caster advice:
let us know... i'd suggest one or two other options if you're open to them, and i suspect others would as well.
I think crossblooded can be well worth it, IF you can take Experimental Spellcaster feat for the Words of Power optional system. That gives you an effect word known for every spell level, countering the otherwise crippling penalty to spells known.
Whether crossblooded or not, picking a race with alternate favored class bonus is practically required, especially as the group's only arcane caster.
Otherwise a big +1 to that last post.
cross blooded is for sorcerers who want to not be casters and want very specific things from two bloodlines, crossblooded is not a boon to a caster. go heritage feat tree if you want another blood line.
If you're interested in pursuing other classes, maybe a Dark Tapestry Oracle would be better than a Sorcerer? Dual-Cursed archetype gets you Misfortune which is always good for debuffs; the mystery comes with some really nice control spells with Black Tentacles and Dust of Twilight and has a revelation that gives you 60 ft. fly speed that lasts long enough to basically always use.
since you're open to other casters...
a witch could be pretty handy. they have a lot of the same issues as wizards in terms of spell preparation but their hexes are super useful and can be used repeatedly so they don't have to worry as much about resource management.
in terms of an ultimate caster though, there's few options that can rival a mystic theurge... this would require a lot more work on your part (since you'd have to pick/learn a lot more spells), but an emberkin aasimar wizard 2 can take 1 level of cleric with either the trickery domain or the fate inquisition and start leveling as a Mystic Theurge at 4th (spell-like abilities count as spells for feats and prestige classes, so you get 2nd level arcane from pyrotechnics and 2nd level divine from mirror image or augry). so, at 10th level you'd only cast as a 9th level wizard, but you'd also cast as an 8th level cleric! focus your stat points/items on Int and think of yourself primarily as a wiz, but you also have all those divine spells to fill in some of your utility casting and give options a normal wizard wouldn't have. for starting stats i'd go with something like: Str 12, Dex 15, Con 14, Int 18 (16+2race), Wis 16, Cha 14 (12+2race).
the arcanist from the Advanced Class Guide playtest might be worth looking at too- its kind of in between a wizard and a sorcerer and (IMO) has more flexibility than either. they're probably the easiest full caster to get right because like a sorcerer they can use each spell as the need arises instead of burning it up too soon, but like a wizard they can change the spells they have access to each day if one isn't really working out or they know they'll have a special need.